Complain

I paid this guys online on the 6 of April in advance for 2of may, then boom come may I didnt pay coz I already paid in advance on the 6th of April ...the next thing I get endless phone calls from their call center telling me I didnt pay even though I explained to kbe agent to another what happened...then got double charged even though they picked up my payment, to my surprise the buying power was even increased without my authorization what a wow this is my last month and I'm paying it and closing....this guys are doing this for the 2nd time to me