Пользователь
We use I will when we have just decided.
A: Lisa called you.
B: Oh, I will call her back.
We use I'm going to when we have decided but not arranged.
B: Yes, I know, I'm going to call her back.(he decided, but not arranged)
We use I'm doing when we have decided and arranged it.
A: When are you meeting Ann this evening?
B: I'm meeting her at 10 p.m.
Some extra sentence:
I'll have to think carefully about how we're going to do this.( He just decided to think about arrange that they've decided already)
We use I will when we have just decided.
A: Lisa called you.
B: Oh, I will call her back.
We use I'm going to when we have decided but not arranged.
A: Lisa called you.
B: Yes, I know, I'm going to call her back.(he decided, but not arranged)
We use I'm doing when we have decided and arranged it.
A: When are you meeting Ann this evening?
B: I'm meeting her at 10 p.m.
Some extra sentence:
I'll have to think carefully about how we're going to do this.( He just decided to think about arrange that they've decided already)