Locking of my line

Why is CellC locking my phone? Having agreed with me that my phone would not be locked, they lock it and its impossible to get hold of the person who has made these promises. My previous complaint on dropping the data charges have been addressed and resolved thanks to Mohamed Cassiem but it doesn't help when they lock the line as well. They are still to send me an updated bill. I have tried contacting Mohamed Cassiem since Monday who has assured me that my line would be open and there has been no answer from his side. CellC is seriously inconveniencing me. May I ask that Mohamed Cassiem please contact me regarding the above issues.