Expired Contract - wont allow me to port number

My Contract expired in April. I am taking out a contract with MTN. When I cancelled my contract I was told by the call centre that I would not be able to port my number until 29th January as I was now on month to month. My contract had expired and I need to give a months notice. I explained that I needed my new phone urgently as I am a pensioner and need a working phone...my existing iPhone 5 is barely working. They said that due to ' Terms and conditions ' they would decline the porting of my number until the months notice was up. I agreed to pay for January but explained the urgency of getting this done immediately. They insisted that there was nothing they could do to help me and that I would just have to wait until the end of January. I find this unacceptable as the contract I signed expired in April. I have not signed or agreed to any further contract but they won't allow me to port my number. My daughter had the same contract with Cell C, which also expired in April and it took a few days to port her number to MTN. She did this when the new iPhone 6 came out so what has changed since then? Can somebody please help me with this? It's URGENT!