Jeg opsiger mobilabonnementet, hvis oprettelsesgebyret ikke står i abonnementsvilkårene.

Because Danish normally writes compound nouns as a single word.

So:

• mobil = mobile
• abonnement = subscription
• mobilabonnement = mobile subscription
• mobilabonnementet = the mobile subscription

This is very common in Danish. Where English often uses two or more words, Danish often joins them into one noun.

Other compounds in the sentence work the same way:

• oprettelsesgebyr = setup/creation fee
• abonnementsvilkår = subscription terms/conditions

Here -et is the definite ending, meaning the.

Both mobilabonnement and oprettelsesgebyr are et-nouns (neuter nouns), so their definite singular form ends in -et:

• et mobilabonnement = a mobile subscription

• mobilabonnementet = the mobile subscription

• et oprettelsesgebyr = a setup fee
• oprettelsesgebyret = the setup fee

Unlike English, Danish usually adds definiteness to the end of the noun instead of using a separate word like the.

Because in Danish, the definite article is usually attached to the noun.

So instead of saying something like the subscription, Danish typically says:

• abonnementet = the subscription

This is the normal pattern when the noun stands by itself.

A separate definite word such as den/det/de is mainly used when there is an adjective or some extra specification before the noun, for example:

• det dyre abonnement = the expensive subscription

But in your sentence there is no adjective before mobilabonnementet, so the ending alone is enough.

Because abonnementsvilkårene is definite plural, not singular.

• vilkår = term / terms
• vilkårene = the terms

So:

• abonnementsvilkår = subscription terms
• abonnementsvilkårene = the subscription terms

The ending -ne is a common definite plural ending in Danish.

Also, vilkår is one of those nouns where the singular and plural indefinite forms look the same, so the definite form vilkårene helps show clearly that it is plural.

That -s- is a linking sound often used in Danish compounds.

So the word is built like this:

• abonnement = subscription
• vilkår = terms/conditions
• abonnementsvilkår = subscription terms

That -s- does not mean possession in the English sense. It is just a normal way of joining the parts of some compound nouns in Danish.

You will see this a lot, for example in words like:

• arbejdsdag = workday
• livsglæde = joy of life
• sundhedssystem = healthcare system

There is not always a simple rule for when the linking -s- appears, so it is often best to learn compounds as whole words.

Yes, Danish has both at opsige and at sige op, and they are related.

In this sentence, opsiger is a good choice because it sounds formal and fits business or contract language well. It often means terminate, cancel, or give notice on something like:

• a contract
• a subscription
• a rental agreement

You can also hear sige op, but opsige often feels more written, official, or legal.

So:

• Jeg opsiger mobilabonnementet = I cancel/terminate the mobile subscription

This is a very natural phrasing in formal Danish.

Because Danish often uses the present tense for future meaning, especially when the situation is clear from context.

Here the sentence means something like:

• I cancel / I will cancel the mobile subscription if...

The hvis clause makes it clear that the cancellation depends on a future condition, so Danish does not need a special future form.

This is very common. Danish often uses the present where English might prefer will.

Hvis means if and introduces a condition.

So the structure is:

• main clause: Jeg opsiger mobilabonnementet
• condition: hvis oprettelsesgebyret ikke står i abonnementsvilkårene

This is the normal Danish word for a real condition, just like English if.

Because this is a subordinate clause, introduced by hvis.

In Danish subordinate clauses, sentence adverbs like ikke normally come before the finite verb.

So:

• main clause: Oprettelsesgebyret står ikke i abonnementsvilkårene.
• subordinate clause: hvis oprettelsesgebyret ikke står i abonnementsvilkårene

This is an important word-order difference in Danish:

• main clause: verb before ikke
• subordinate clause: ikke before verb

That is exactly what you see here.

Yes, literally står means stands, but in Danish stå i is often used idiomatically to mean:

• be stated in
• be written in
• appear in
• be listed in

So:

• oprettelsesgebyret står i abonnementsvilkårene
  = the setup fee is stated/listed in the subscription terms

This is a very natural Danish way to talk about something being mentioned in a document, contract, rules, or terms.

Because hvis oprettelsesgebyret ikke står i abonnementsvilkårene is a subordinate clause, and many Danish writers put a comma before such clauses.

So the comma separates:

• Jeg opsiger mobilabonnementet
• hvis oprettelsesgebyret ikke står i abonnementsvilkårene

You may also see Danish written without this comma, depending on which comma system is being followed, but the comma in your sentence is completely normal and correct.

The sentence has two parts:

1. Jeg opsiger mobilabonnementet
   This is the main clause.

2. hvis oprettelsesgebyret ikke står i abonnementsvilkårene
   This is the subordinate if-clause.

So the full pattern is:

• Main clause + subordinate clause

Inside the main clause, Danish follows the usual main-clause pattern with the verb in second position:

• Jeg = subject
• opsiger = finite verb
• mobilabonnementet = object

Inside the subordinate clause, the order changes:

• hvis = subordinating conjunction
• oprettelsesgebyret = subject
• ikke = sentence adverb
• står = finite verb
• i abonnementsvilkårene = prepositional phrase

That contrast between main-clause word order and subordinate-clause word order is one of the key grammar points in this sentence.