Misinforming client causes two problems for client

I have a contract with cellc, i received a phone call from cellc sales offering me a secondary contract and AGMobile tablet. I accepted and asked them to port my 084 prepaid Virgin Mobile number to CellC contract. They agreed and did it.. Upon delivery i found the device had a factory fault. ellc call centre advised me to return the device and choose between them resending me the same model or choose another brand. If i chose the same model they would arrange delivery. If I wanted another brand, they would cancel the current secondary line so that I may open a new contract immediately after cancellation. I agreed to cancel and take different device in the same price range. CellC called me to confirm that indeed there was factory fault in the device and my secondary contract has been successfully cancelled. I was ready to open new contract as promised and choose a different device. Thats when they decided to inform me that cancelling the contract has affected my credit (ITC) score negatively and i can no longer take a contract. Firstly why did they advise me to cancel yet didnt inform me that my credit score would be affected? Secondly they say i cant have my 084 number back anymore