Wrong Billing, Poor service

I upgraded my contract and during the upgrade, i was advised that I can carry over the old device. Now Telkom is billing me for the old device yet they did not give me a new device. I have been to the Telkom shop and they have escalated to the billing office. The accounting department has not been responsive to me or to the shop and it is frustrating to keep following up on a matter which the shop acknowledges its a mistake in the billing system and I have to spend so much time to get this corrected.