Questions & Answers about Ich telefoniere mit meiner Mutter.
Why does it say Ich telefoniere instead of a literal translation for 'I am on the phone'?
German does not have a separate '-ing' tense (present continuous) like English does. The simple present tense Ich telefoniere covers both 'I talk on the phone' and 'I am talking on the phone'.
Why is it meiner Mutter instead of meine Mutter?
The preposition mit always forces the following noun into the dative case. Because Mutter is a feminine noun, the possessive word meine changes its ending to become meiner in the dative case.
Could I use the verb anrufen (to call) here instead?
They mean slightly different things! Ich rufe meine Mutter an means 'I am calling my mother' (as in, dialing her number right now). Ich telefoniere mit meiner Mutter means the call has already connected and you are actively having a conversation with her.
Do I always have to use mit to say who I am talking to?
Yes, the verb telefonieren strictly requires the preposition mit (plus the dative case) when you mention your conversation partner. You cannot just say Ich telefoniere meine Mutter.