I have a Motorola Moto G, 3rd Gen, running Marshmallow. For some months, it's been fine, but for a week now, every time I try to make a landline call, I get "Network busy" every single time. Other phones in the house connect every time, and other networks' SIMs also work perfectly every time with my phone. I can call mobiles OK and both mobiles and landlines can call me. I can also make landline calls away from home, but every landline call with my SIM at home fails. I've re-started the phone, manually re-selected the network, run the phone in safe mode cleared the cache and force-stopped the phone app. I'm reluctant to factory-reset my phone, as I don't believe it will help. My provider (the Post Office, via EE) have been helpful, but they now say the problem is signal strength in my home area, and there's no more they can do. I don't know if this makes sense when I can receive mobile and landline calls fine and every other phone in the house (different providers, but all EE) work perfectly. I'd like to stay with PO as their customer service is so good, but is my only option now a PAC code?