Miałam oddzwonić do mamy, ale telefon był rozładowany i nie było zasięgu.

Miałam is the past tense, feminine singular form of mieć.

• miałam = I had / I was supposed to (said by a woman)
• miałem = the same, but said by a man

So if the speaker is female, she says miałam oddzwonić.

Not quite. In this sentence, mieć + infinitive often means:

• to be supposed to
• to have intended to
• to have been expected to

So miałam oddzwonić do mamy means something like:

• I was supposed to call my mom back
• I meant to call my mom back

It is softer than musiałam oddzwonić, which would mean I had to call my mom back.

Because oddzwonić means to call back / return a phone call.

Compare:

• zadzwonić = to call / to phone
• oddzwonić = to call back

So if someone called earlier and you are returning the call, oddzwonić is the natural choice.

Also, oddzwonić is perfective, so it refers to one completed action: to call back once / successfully.

Mamy is in the genitive case because the preposition do requires the genitive.

• mama = nominative
• do mamy = to mom / to my mom

This is normal after dzwonić do kogoś and oddzwonić do kogoś.

Examples:

• Dzwonię do taty. = I’m calling dad.
• Oddzwonię do mamy. = I’ll call mom back.

Because Polish does not choose case only by English meaning. It depends heavily on the preposition and the verb pattern.

Here the structure is:

• dzwonić / oddzwonić do + genitive

So:

• do mamy is correct
• mamie would be dative, but that is not the pattern used here

Even though English says to mom, Polish uses do mamy, not dative.

Literally, it means the phone was discharged.

In natural English, that usually means:

• the phone battery was dead
• the phone had no charge

Rozładowany is a past participle/adjective from rozładować and is often used for things like:

• telefon rozładowany = a dead phone
• bateria rozładowana = a drained battery

Because telefon is masculine singular, the form is rozładowany.

Nie było zasięgu is the normal Polish way to say:

• there was no signal
• there was no coverage

It uses the impersonal structure:

• było = there was
• nie było = there wasn’t / there was no

This is very common in Polish for saying something existed or did not exist.

So:

• Był problem. = There was a problem.
• Nie było czasu. = There was no time.
• Nie było zasięgu. = There was no signal.

Because after nie było in this kind of existential sentence, Polish usually uses the genitive.

Here:

• base form: zasięg = signal / range / coverage
• genitive singular: zasięgu

So:

• Był zasięg. = There was signal.
• Nie było zasięgu. = There was no signal.

This is a very important pattern in Polish:

• jest + nominative
• nie ma / nie było + genitive

Examples:

• Jest czas. / Nie ma czasu.
• Był prąd. / Nie było prądu.

Here zasięg means phone signal, reception, or network coverage.

So nie było zasięgu means:

• there was no signal
• there was no reception
• there was no coverage

In other contexts, zasięg can also mean range more generally, but with phones it usually means signal/coverage.

They are doing two different jobs grammatically.

1. telefon był rozładowany

This is a normal sentence with a subject:

• telefon = subject
• był = masculine singular past of być
• rozładowany = adjective matching telefon

So był agrees with telefon.

2. nie było zasięgu

This is an impersonal existential structure:

• literally: there was no signal
• było is the fixed neuter singular form often used in this pattern

So było here does not agree with zasięgu in the same way as był agrees with telefon.

Yes, but the meaning changes slightly.

Original:

• Miałam oddzwonić do mamy, ale telefon był rozładowany i nie było zasięgu.

This sounds like:

• I was supposed to call my mom back, but my phone was dead and there was no signal.

If you use bo:

• Miałam oddzwonić do mamy, bo telefon był rozładowany...

that would sound odd, because bo means because, and a dead phone is not the reason you were supposed to call back. It is the reason you couldn’t.

So ale is the right connector here: it shows contrast between intention/obligation and reality.

Yes, this word order is natural and idiomatic.

The sentence flows well:

• Miałam oddzwonić do mamy = what the speaker intended/was supposed to do
• ale = contrast
• telefon był rozładowany i nie było zasięgu = why it did not happen

You could change the order for emphasis, for example:

• Miałam oddzwonić do mamy, ale nie było zasięgu i telefon był rozładowany.

This is also correct, but it emphasizes the lack of signal first. The original version sounds very natural in everyday speech.

Yes. It may sound slightly redundant in some contexts, but it is absolutely natural.

It suggests there were multiple problems:

• the phone battery was dead
• there was no signal/coverage anyway

So the speaker is reinforcing the idea that calling back was impossible.

In casual speech, people often pile up reasons like this, especially when explaining why they could not call.