How Much do you know of your company

I placed an order on the 22 of October 2016 with Telkom as i moved premises. It took me over R500 of airtime and uncountable hours on the phone trying to resolve the issue. 1 month later is when my phone is sorted out but only to find a bill of R1300 that i cannot dispute because the system that they have in place will not accept my dispute logging. Question is, do i pay or just leave them to black list me?