City of cape town billing debacle.

I bought a house recently. The city decided to bill the old owner for months AND at the same time billed me (doubled billed!!!), but did not send any notice to me despite me applying for emailed invoices. There is a credit on the old account which I paid and city is refusing to transfer the credit despite me suppling the evidence of having paid it, with bank statements. They acknowledge that there is a credit, but refuse to transfer it. I spoke to a call center agent and comp**** with their instructions, only to be told that the evidence was not sufficient and that I must resubmit the evidence. They are now threatening to cut off my electricity supply.