I can't call my old sim back because I already had called him back before the task came. Now it does not work?

Please clarify your question as it makes little sense.

Urban Dictionary: sim

Maybe she means the game.

Moved to video games since this does look like a question about a game.

Agnesmarie, can you give us more details such as which game you are playing and which platform you are playing on? It might help us know where to begin in giving you advice.

For "Call an old Sim back" quest, just have you Sim use the phone, there is an "call old sim" option. 10 hrs