Double bill and initial contract breach

I was promised when i took out the ADT contract that for the first 2 months i would not be billed as i paid the joining fee cash. I have been billed from the start. I tried to contact the Sales person Leon Solomon who promised he will sort out but he just does not come back to me. This month i was billed beginning of the month and now today again.<br> What do i need to do to sort this out ???