MTN refuse to refund my credit on pay as you go

I have had an MTN mobile number for over 25 years and use predominately for business. Due to CODID 19, I have had no business and have not used my phone for several months. MTN have deactivated my phone and refuse to refund the R2500 held in credit as Pay as you Go. They state that contract states that no refund is possible and my number is allocated elsewhere. I do not believe and this is nothing but pure theft. Peter Stephenson