Operator ima tarifni paket i unaprijed plaćenu uslugu bez obračunskog razdoblja.

Because both phrases are direct objects of ima, so they are in the accusative case.

The difference is due to gender:

• tarifni paket is masculine inanimate singular, and in Croatian the accusative form of masculine inanimate nouns is usually the same as the nominative.
• unaprijed plaćena usluga is feminine singular, so in the accusative it changes to unaprijed plaćenu uslugu.

So:

• nominative: tarifni paket, unaprijed plaćena usluga
• accusative: tarifni paket, unaprijed plaćenu uslugu

It is in the genitive case because the preposition bez always takes the genitive.

Dictionary form:

• obračunsko razdoblje = nominative singular

After bez:

• bez obračunskog razdoblja = genitive singular

Both the adjective and noun change:

• obračunsko → obračunskog
• razdoblje → razdoblja

The basic dictionary form is unaprijed plaćena usluga.

In the sentence it becomes unaprijed plaćenu uslugu because it is accusative singular feminine.

You can think of it like this:

• nominative: unaprijed plaćena usluga
• accusative: unaprijed plaćenu uslugu

This is a very common adjective + noun agreement pattern in Croatian.

Unaprijed is an adverb meaning in advance or ahead of time.

It does not change form. It modifies plaćenu and helps create the idea of prepaid:

• plaćena usluga = paid service
• unaprijed plaćena usluga = prepaid service

So unaprijed stays the same regardless of case, gender, or number.

Because Croatian adjectives must agree with the nouns they describe in:

• gender
• number
• case

Here are the matches:

• tarifni paket
  
  • masculine singular, accusative
• plaćenu uslugu
  
  • feminine singular, accusative
• obračunskog razdoblja
  
  • neuter singular, genitive

So the different endings are not random; they show grammatical agreement.

No. Croatian does not use articles like English a/an or the.

So Operator ima tarifni paket... can mean things like:

• The operator has a tariff package...
• An operator has the tariff package...

The exact meaning depends on context, not on an article.

I means and and connects the two direct objects of ima:

• tarifni paket
• unaprijed plaćenu uslugu

So the structure is:

• Operator = subject
• ima = verb
• tarifni paket i unaprijed plaćenu uslugu = two coordinated objects
• bez obračunskog razdoblja = a prepositional phrase modifying the second object, or possibly the service description as a whole depending on context

Grammatically, it most naturally attaches to the nearest phrase, so a learner will usually read it as describing unaprijed plaćenu uslugu.

So the most natural reading is:

• a tariff package and a prepaid service without a billing period

If the speaker wanted to make it clearer that without a billing period applies to both items, Croatian would often restructure the sentence.

Yes. Croatian word order is more flexible than English because case endings show grammatical roles.

This sentence uses a neutral, straightforward order:

• Operator ima tarifni paket i unaprijed plaćenu uslugu bez obračunskog razdoblja.

You could change the order for emphasis, for example:

• Operator ima unaprijed plaćenu uslugu bez obračunskog razdoblja i tarifni paket.

That is still grammatical, but the emphasis changes. The original version sounds more neutral and natural for a plain statement.

Here are the main dictionary forms:

• operator = operator
• imati = to have
• tarifni paket = tariff package / plan
• usluga = service
• unaprijed plaćen = prepaid / paid in advance
• obračunsko razdoblje = billing period

And the forms used in the sentence are:

• ima = 3rd person singular present of imati
• tarifni paket = accusative singular
• unaprijed plaćenu uslugu = accusative singular feminine
• obračunskog razdoblja = genitive singular after bez