Мобільний оператор змінив тарифний план.

Both мобільний and тарифний are adjectives in the masculine singular nominative form, because they describe masculine singular nouns:

• оператор = operator
• план = plan

In Ukrainian, adjectives must agree with the noun they modify in gender, number, and case.

So:

• мобільний оператор = mobile operator
• тарифний план = tariff plan / pricing plan

The ending -ий is a very common ending for masculine nominative singular adjectives.

змінив is the past tense masculine singular form of the verb змінити, which means to change.

Ukrainian past tense agrees with the subject in gender and number:

• він змінив = he changed
• вона змінила = she changed
• воно змінило = it changed
• вони змінили = they changed

Here the subject is оператор, which is a masculine singular noun, so the verb is змінив.

This is about aspect, which is very important in Ukrainian verbs.

• змінити = perfective aspect, meaning to change as a completed action
• змінювати = imperfective aspect, meaning to be changing, to change repeatedly, or focusing on the process

In Мобільний оператор змінив тарифний план, the sentence presents the action as a completed fact: the operator changed the plan.

So змінив is the natural choice.

Compare:

• Оператор змінив тарифний план. = The operator changed the plan.
• Оператор змінював тарифний план. = The operator was changing the plan / used to change the plan.

Yes, it does change in terms of case, but in this sentence only the adjective shows it clearly.

The phrase тарифний план is the direct object of the verb змінив, so it is in the accusative case.

For masculine inanimate nouns in Ukrainian, the accusative singular is usually the same as the nominative singular.

So:

• nominative: тарифний план
• accusative: тарифний план

They look identical here.

That is why the phrase does not visibly change, even though grammatically it is in the accusative.

You know this from a combination of meaning, word order, and grammar.

1. Meaning: an operator can change a tariff plan; a tariff plan does not usually change an operator.
2. Verb relationship: змінити takes a direct object, and тарифний план fits that role.
3. Word order: Ukrainian word order is flexible, but the most neutral order is subject + verb + object, which is exactly what we have here:
   • Мобільний оператор = subject
   • змінив = verb
   • тарифний план = object

Yes. Ukrainian allows more flexibility in word order than English. You could also say:

• Тарифний план змінив мобільний оператор.

This still means The mobile operator changed the tariff plan, not The tariff plan changed the mobile operator, because context and case help identify the roles.

However, the original sentence:

• Мобільний оператор змінив тарифний план.

is the most neutral and standard way to say it.

Different word order can add emphasis:

• Тарифний план змінив мобільний оператор. = It was the tariff plan that the mobile operator changed.
• Змінив мобільний оператор тарифний план. = more marked, less neutral, often stylistic or conversational

Not exactly, but it is close.

Мобільний оператор literally means mobile operator or mobile network operator. In many contexts, English would naturally say:

• mobile operator
• cellular provider
• mobile carrier
• phone company

So the exact translation depends on context.

Тарифний план is the standard phrase for a service pricing plan, especially for telecom services. Depending on context, it can mean:

• tariff plan
• pricing plan
• service plan
• mobile plan

In everyday English, people often just say plan, as in They changed my plan.

In Ukrainian, тарифний план sounds normal and specific.

A simple pronunciation guide is:

Mobilʹnyy operator zminyv taryfnyy plan

A rough English-style approximation:

moh-BEEL-nyy oh-peh-RAH-tor zmi-NYV tah-RYF-nyy plahn

A few useful notes:

• і sounds like ee in see
• и is a short central vowel, not exactly like any single English vowel
• зм at the start of змінив may feel unusual for English speakers, but it is normal in Ukrainian
• stress:
  • мобільний
  • оператор
  • змінив
  • тарифний
  • план

Ukrainian does not have articles.

So Ukrainian nouns do not have separate words for:

• a
• an
• the

Whether something is definite or indefinite is understood from context.

So:

• Мобільний оператор змінив тарифний план.

could be interpreted in English as:

• The mobile operator changed the tariff plan
• A mobile operator changed a tariff plan
• The mobile operator changed a tariff plan

The correct English version depends on the situation.

Yes. Оператор can mean different things depending on context, including:

• an operator as a person
• a company or provider, especially in telecom contexts
• a machine operator or technical operator in other contexts

In мобільний оператор, it usually means a mobile service provider/company, not an individual person.

Yes, it is fully natural and grammatical.

It is a clear, neutral sentence in standard Ukrainian:

• Мобільний оператор = subject
• змінив = completed past action
• тарифний план = direct object

It sounds like something you might see in a customer service message, a complaint, or a news/reporting context.

Yes, in many everyday contexts you could hear:

• Мобільний оператор поміняв тарифний план.

This is understandable and common in speech, but змінив is usually a bit more standard and neutral in formal or written language.

Very roughly:

• змінив = more neutral, standard
• поміняв = more conversational

So the original sentence is a very good model for learners.