Unfair billing / horrible service

I didn’t have internet for about 12 days last month and 2 days this month but plus I didn’t get the speed I was promised for. Now they want me to pay the full bill that not fair. I phoned several times about this but still no help. All the following references number are the proof- 306953, ***,***,***,***,*** and about 5 calls I didn’t get the reference number but it good cause they got records for all the calls.