Operator šalje SIM karticu.

Because SIM karticu is the direct object of the verb šalje (sends / is sending), so it has to be in the accusative case.

• kartica = nominative singular
• karticu = accusative singular

Since kartica is a feminine noun ending in -a, its accusative singular usually changes to -u.

So:

• SIM kartica = a/the SIM card as the subject
• šalje SIM karticu = is sending a/the SIM card as the object

Operator is in the nominative singular because it is the subject of the sentence — the one doing the action.

So the structure is:

• Operator = subject, nominative
• šalje = verb
• SIM karticu = object, accusative

Šalje is the 3rd person singular present tense of slati, meaning to send.

So operator šalje means:

• the operator sends
• or the operator is sending

In Croatian, the present tense can often cover both the simple present and the present continuous, depending on context.

Croatian does not have articles like English a/an and the.

So Operator šalje SIM karticu could mean:

• The operator sends a SIM card
• The operator sends the SIM card

Which one is meant depends on the context.

Yes. Croatian word order is more flexible than English because cases show the grammatical roles.

The neutral, straightforward order is:

• Operator šalje SIM karticu.

But you could also hear:

• SIM karticu šalje operator.
• Šalje operator SIM karticu.

These versions may sound more marked or emphasize different parts of the sentence, but the basic meaning stays the same because the cases show who is doing what.

No. In this sentence, SIM stays the same.

The case ending appears on kartica:

• SIM kartica
• SIM karticu

So SIM acts like an unchanged modifier, while kartica is the noun that actually changes form.

A rough pronunciation is shal-ye.

More precisely:

• š sounds like sh in shoe
• a is like a in father
• lj is a special Croatian sound, somewhat like lli in some pronunciations of million, or a soft ly
• e is like e in bed, but often a bit cleaner and shorter

So šalje is approximately SHA-lye.

Here operator usually means a mobile network operator / carrier / provider, not a telephone switchboard operator.

So in this context, it means the company that provides the SIM card, such as a mobile phone company.

Yes. Kartica is feminine singular.

You can tell because:

• it ends in -a, which is very common for feminine nouns
• its accusative singular becomes karticu, which is also typical for feminine nouns of this type

This matters because adjectives and some other words would agree with it in gender, number, and case.

That would be a different verb form and usually a different meaning.

• šalje comes from slati and is imperfective
• pošalje comes from poslati and is perfective

In many contexts:

• šalje = is sending / sends
• pošalje = sends off / manages to send / will send depending on context

So for a simple neutral present-tense statement, Operator šalje SIM karticu is the safest choice.