Double billing!!!!

I moved my line to a smarthome Essential but for some reason Telkom decide to bill me for two ADSL services when I only have one. I have contacted billing (ref no. ***2) and when they put me through to retentions I get no answer after 20 mins of holding. This is after numerous counts of pathetic service just to migrate my line which took over 3 months to sort out. I am refusing to pay a cent more than the amount of R 429 which was specified on my contract until this is sorted out and Telkom have the nerve to charge me interest due to their incompetence