Eu chamei a polícia.

Yes. In Brazilian Portuguese, subject pronouns are often omitted when the verb already makes the subject clear.

• Eu chamei a polícia. = correct
• Chamei a polícia. = also correct and very natural

Including eu can add emphasis, contrast, or clarity, for example:

• Eu chamei a polícia, não ele.
  I called the police, not him.

Chamei is the first person singular form of chamar in the pretérito perfeito (simple past / preterite).

So:

• chamar = to call
• eu chamei = I called

This tense is used for a completed action in the past.

Examples:

• Eu chamei um táxi. = I called a taxi.
• Eu chamei minha irmã. = I called my sister.

Because chamar is an -ar verb, and in the preterite, the eu form usually ends in -ei.

For chamar:

• eu chamei
• você/ele/ela chamou
• nós chamamos
• vocês/eles/elas chamaram

So -ei is a very common ending for I in the past with -ar verbs:

• falei = I spoke
• comprei = I bought
• trabalhei = I worked

Because chamar normally takes a direct object.

You call someone/something directly:

• chamar a polícia
• chamar um médico
• chamar um táxi

So here:

• a polícia = the direct object

Using para would change the structure and usually suggest something more like calling to someone rather than calling/summoning them.

In Portuguese, a polícia is usually treated as a singular feminine noun referring to the police as an institution or force.

So:

• a polícia chegou = the police arrived
• a polícia foi chamada = the police were called

If you want to talk about individual police officers, you would usually say:

• os policiais = the police officers / the cops

So:

• Eu chamei a polícia. = I called the police.
• Eu chamei os policiais. = I called the police officers.

Because the noun polícia is grammatically feminine in Portuguese, so it takes:

• a polícia
• a polícia brasileira
• essa polícia

This is a grammar feature, not something based on real-world gender.

Many nouns ending in -a are feminine, and polícia is one of them.

In this sentence, yes, a polícia is the normal and natural form.

Portuguese often uses articles where English may not focus on them as much. Here, a polícia refers to the police as a known service/institution.

So:

• Eu chamei a polícia. = natural
• Eu chamei polícia. = not standard in this context

Not exactly.

• chamar a polícia means to call/summon the police
• ligar para a polícia means to phone the police

In many situations, chamei a polícia strongly suggests that you contacted them so they would come, whether by phone or another method.

If you specifically want to emphasize the phone call itself, liguei para a polícia is more precise.

In Brazilian Portuguese, chamei is approximately:

• sha-MEI

A few details:

• ch in Brazilian Portuguese usually sounds like English sh
• the stress is on -mei
• ei here sounds roughly like ay in say

So chamei sounds roughly like sha-MAY.

The accent in polícia shows the stressed syllable:

• po-LÍ-ci-a

So the stress is on lí.

The accent mark is important because it tells you how to pronounce the word correctly. Without it, the stress pattern would be unclear or wrong.

That would mean something different.

• Eu chamei a polícia. = I called the police.
  A completed action.
• Eu chamava a polícia. = I used to call / I was calling the police.
  An ongoing, repeated, or background action in the past.

So if you mean one finished event, chamei is the correct form.

No. Chamar is a very common verb with several uses. It can mean:

• to call / summon
  Chamei um médico.
• to call out to
  Chamei meu amigo da janela.
• to be called / named
  Eu me chamo Ana.

In Eu chamei a polícia, it means to call/summon.