customer since 1989, bills 1/3 high this month and NO HELP

My elderly mom has comcast internet to keep her landline. she has been a customer since 1989. her bill has been 76.00 for some time, now 106.00! i have called and talked to agents about lowering the bill with no help, i have been on hold or fruitless phone calls for a total of 4 hours, talked to supervisors, etc. I have the same set up through ATT for $70 - just negotiated with them and it took 10 minutes. Why can comcast to the same? all i got were convoluted answers "you will be eligible for a small credit but i can't tell you when" . I will be ending her service  - this is the last straw. Your customer service is non-existent.