Bad service from MTN

I've been calling MTN For a week requesting my old number because I was hospitalized hence I was not using the number. I was given hope by the agents I spoke to now the supervisor Lindo is telling me nonsense just coz he want me to go off the line. I feel that MTN has failed me coz every is connected to that number. And I have been using this number for years and years now I have to change a number