How do I speak with someone about overcharging on my bill?

I spoke with someone last month when I saw you were doubling my service from 40 to 80 when I was still in the plan for 40 a month. they apologized and said id be credited 40 back to my account and that i could move into an affordable program. I was not move into the affordable program my card was charged 80 causing an overdraft which you then charged me an additional late fee for and continued to charge my 75 for the following month, after I explained I dont have that much a month. I been a customer for over 8 years, I can see you have a 40 a month plan, so why are you lying about crediting me back and moving me into a plan? and why cant I reach anyone about this? I see astound offers 30 a month for faster speed, should I switch?