Landline Phone Troubleshooting

I a ready to throw this phone in the garbage. It rings in house only three times before it goes to voicemail, the caller says it rings from them 5 times, Now it goes directly to voicemail. It used to have the area code when you redial, now it doesn't. I tried to reprogram but to no avail. It is so

Hi no one can call my elderly mom on her att landline - everyone gets the message saying you have to dial a 1 or all 10 digits. I live out of state so every call is long distance. I am dialing 1 and then 10 digits every time. This has been ongoing since November!  Att has been of little help

I am a developer who is dividing a parcel of land into 17 residential lots in an exisitng neighborhood.  We want to request At&t to install service within this residential subdivision.  Please let me know who to contact.