MTN discriminates against people BASED ON AGE.

I currently have a data contract with MTN. Lately I find that the allocated data is not enough, and I then app**** for an extra contract. When the consultant (lady) phoned me, after asking for confirmation of details, she informed me that I could not get a contract because I was TOO OLD. I then asked her why I was TOO OLD now, when 18 months ago I was still eligible for a contract. While I was still talking to her regarding the matter, she just hung up on me. I am 73 years old. Isn't there a law which protects older people against **************?