Net omdat aanmanings kom, beteken dit nie dat vervaldatums verander nie.

Net omdat means just because or simply because.
Here net does not mean clean or only a literal just on its own; together with omdat, it forms the expression just because.

It introduces a reason that is not enough by itself to justify the conclusion.

Yes. The sentence has three main parts:

• Net omdat aanmanings kom = Just because reminders arrive
• beteken dit nie = it does not mean
• dat vervaldatums verander = that due dates change

So the pattern is:

• subordinate clause
• then main clause
• then a dat-clause explaining what is supposedly meant

Afrikaans often uses dit and the two-part negative nie ... nie in structures like this.

Because Net omdat aanmanings kom is an introductory subordinate clause.
In Afrikaans, when a subordinate clause comes before the main clause, it is normally separated by a comma.

So:

• Net omdat aanmanings kom, = subordinate clause
• beteken dit nie ... nie. = main clause

Aanmanings is the plural of aanmaning. It usually means reminders, payment reminders, or sometimes stronger notices such as dunning notices or follow-up notices.

The exact English word depends on context, but in administrative or billing language it often refers to reminders sent when action or payment is expected.

Kom literally means come, but like English, Afrikaans can use come for things that arrive or are received.

So aanmanings kom means something like:

• reminders come in
• reminders arrive
• reminders are sent/received

It is a normal and natural use of kom.

Afrikaans often uses dit in the same kind of structure where English uses it:

• it does not mean that ...
• dit beteken nie dat ... nie

So dit here is not referring to one specific object. It is a structural or anticipatory it, pointing forward to the dat-clause.

Because standard Afrikaans negation is often a two-part negative:

• first nie appears earlier in the clause
• second nie appears near the end of the whole clause

Here you get:

• beteken dit nie ... nie

That is the normal way to say does not mean in this kind of sentence.

An important point: the final nie comes after the dat-clause because it closes the whole negative main clause. It does not mean that Afrikaans is separately negating verander here.

After omdat and dat, Afrikaans normally puts the finite verb at the end of the subordinate clause.

In this sentence, though, both subordinate clauses are very short:

• aanmanings kom
• vervaldatums verander

Since each clause only has a subject and a verb, the verb is already at the end anyway, so the word order does not look unusual.

You can see the pattern more clearly in longer examples:

• omdat die aanmanings elke week kom
• dat die vervaldatums later verander

In both cases, the verb comes last in the subordinate clause.

Because the sentence is speaking about these things in general, not about a specific set already identified as the reminders or the due dates.

Afrikaans often leaves out the article in general plural statements, just as English often does:

• Reminders come
• Due dates change

If you wanted to refer to specific ones, you could use die.

Vervaldatums is the plural of vervaldatum.

It is a compound noun:

• verval = expiry / lapse / becoming due
• datum = date

So vervaldatum means due date or expiry date, depending on context.

The plural is formed on the whole compound:

• vervaldatum
• vervaldatums

Not naturally in this exact pattern.

Net omdat is the normal expression for just because.
Want also means because, but it joins main clauses and does not work the same way here.

So:

• Net omdat ... = Just because ...
• want ... = because/for ... in a different sentence structure

In this sentence, omdat is the correct choice.

Because Afrikaans verbs have very little conjugation in the present tense.
Unlike English, Afrikaans usually does not add different endings for different persons.

For example:

• ek kom
• jy kom
• hy kom
• ons kom
• hulle kom

The same is true for verander and beteken in normal present-tense use. That is why the verbs in this sentence stay so simple.