I det fallet väljer jag mobilabonnemanget.

Because Swedish main clauses usually follow the V2 rule: the finite verb comes in the second position.

Here, I det fallet is placed first, so the verb väljer has to come next:

• I det fallet väljer jag mobilabonnemanget.

If you start with the subject instead, then you get:

• Jag väljer mobilabonnemanget i det fallet.

Both are possible, but the first version gives a little more emphasis to in that case.

It is a prepositional phrase:

• i = in
• det = that
• fallet = the case

So literally it is in that case.

The noun is ett fall and in this expression fall means case/situation, not a physical fall.

Because Swedish normally uses the definite form of the noun after demonstratives like den/det.

So:

• ett fall = a case
• fallet = the case
• det fallet = that case

This is very normal in Swedish:

• det huset = that house
• den bilen = that car
• det fallet = that case

For an English speaker, it can feel like Swedish is saying that the case, but that is simply how the grammar works.

Because it refers to a specific mobile plan/subscription, not just any one.

• ett mobilabonnemang = a mobile plan / a mobile subscription
• mobilabonnemanget = the mobile plan / the mobile subscription

So the sentence implies that the speaker is choosing a particular, already identifiable plan.

If you wanted to say a mobile plan, you would say:

• I det fallet väljer jag ett mobilabonnemang.

That would sound less specific.

It is a compound noun, which is very common in Swedish:

• mobil = mobile / cell phone
• abonnemang = subscription / service plan
• mobilabonnemang = mobile subscription / phone plan
• mobilabonnemanget = the mobile subscription / the phone plan

Swedish often builds long nouns this way instead of using separate words.

Yes, you can.

The difference is mostly about focus and style:

• I det fallet väljer jag mobilabonnemanget.
  This puts the situation first: in that case...
• Jag väljer mobilabonnemanget i det fallet.
  This starts more neutrally with I choose...

Both are grammatical. The version with I det fallet first is especially natural when reacting to a previous statement or condition.

They are similar, but not always identical.

• i så fall often means if so / in that case
• i det fallet often points more directly to a specific case/situation

Examples:

• Om det blir för dyrt, väljer jag ett annat alternativ.
  I så fall sounds very natural here: If so, I’ll choose another option.

• Det finns två möjliga scenarier. I det fallet väljer jag mobilabonnemanget.
  Here i det fallet can sound a bit more tied to one particular scenario.

In everyday speech, i så fall is often more common.

It is present tense of välja = to choose.

• jag väljer = I choose / I am choosing

In Swedish, the present tense can also be used for a future decision, depending on context, much like in English:

• I morgon väljer jag abonnemanget.
  = Tomorrow I’m choosing the plan.

So here it is simply the present form.

A rough guide is:

• väljer ≈ VEL-yer

A few important points:

• ä sounds somewhat like the e in bed, though not exactly the same
• lj in väljer is softened; many learners find it tricky
• the j sounds like English y

You do not pronounce it like an English j in job.

Välja is the most direct and standard verb for choose.

Other possibilities exist, but they are slightly different:

• välja = choose
• ta = take, pick
• gå för = go for
• bestämma sig för = decide on

Examples:

• I det fallet väljer jag mobilabonnemanget.
  Very neutral and clear.
• I det fallet tar jag mobilabonnemanget.
  More conversational: I’ll take the mobile plan.
• I det fallet går jag för mobilabonnemanget.
  More informal: I’ll go for the mobile plan.

So väljer is a very good textbook-standard choice.

In normal Swedish, you do need the subject.

So:

• I det fallet väljer jag mobilabonnemanget.

You cannot normally drop jag the way you can in languages like Spanish or Italian.

Swedish usually requires an explicit subject in ordinary statements.

Because Swedish usually puts the definite article at the end of the noun as a suffix.

So:

• abonnemang = subscription
• abonnemanget = the subscription

And in compounds:

• mobilabonnemang = mobile subscription
• mobilabonnemanget = the mobile subscription

This is one of the big differences from English. Instead of a separate word like the, Swedish often adds -en or -et to the noun.

Yes. Fall can have several meanings depending on context, including:

• fall = case
• fall = fall/drop
• fall = grammatical case in linguistics

But in the expression i det fallet, it clearly means in that case / in that situation.

This is a very common expression, so learners should think of it as a set phrase.