Landline caller always gets busy signal when calling me.
My friend calls our T-Mobil Apple Cell phones and always gets a busy signal. (She can call me from her cell phone successfully.) She is calling from an ATT landline. She can call other Apple Cell phones (who are not on T-Mobile) from her landline, just not ours. I have checked my phone for call blocking, call forwarding, airplane mode, do not disturb, etc. And it isn't my phone's settings. Any advice?