MTN Bad Accounts & Service

On 3rd February 2021 I renewed my contact for a further 2 years to take advantage of the better rates. My contract expired 16th February 2021 and I have not taken a new phone. I was advised by the Oakfields Benoni Branch that there was a prorate charge for the 2 weeks. When I received the invoice date 12th February 2021 there was an additional charge of R422.89 for "Migration Fee: Service Level Once off charge". This doubles my monthly cost. The Branch had no knowledge of this charge and raised a query on 14th February 2021. This was not answered and closed by MTN. I was advised to contact MTN directly which I have done 3 times ***. I have had no reply.