Blocked phone very *****

On the 28th of Jan I purchased a grey import Samsung S5 from [URL Removed] The phone was delivered on the 2nd of Feb. I used it without problem until Sat the 7th of Feb when the phone refused to recognise my MTN Sim card. I took the phone to MTN on the 11th of Feb where I was told that the phone had been blacklisted by Telkom Mobile for \bad debt."They also said it wasn't the first phone purchased through [URL Removed] they had seen that had been blacklisted. I phoned [URL Removed] and was told by John that they would collect the old phone and replace it with a working S5. The phone was collected on the 13th of Feb. I have been phoning regularly to find out what is wrong. At first I was told that Telkom mobile must've blacklisted the wrong serial number. Then I was told that there were many [URL Removed] phones with that problem. Then I was told that an e-mail was sent to all call centre staff about the problem. Why did Telkom mobile block the phones and when am I receiving my replacement phone? I am without a phone and can't perform my job! I phone. No supervisor phones me back. I have no answers. Shocking"