Refusing to take my money

Ever since I "upgraded" to an MTN Flexi 100 contract, I have been unable to purchase data bundles. I can't convert the R199 airtime I have into data, nor can I have it added as an extra item on my monthly bill. My usage limit is set at R0, and when I try to change it to anything other than R0 (even just R1), the MyMTN portal says I can't increase the usage limit above the service provider limit. First off, I don't even know what that means. But anyway. And you can't even talk to a callcenter agent anymore, the 135 number merely has a set of menu items to choose from and a little electronic voice reads stuff back at you. None of the options are helpful. That last part is particularly egregious because the MTN app on my phone says to contact MTN for assistance. But the "assistance" doesn't do anything except tell me I have R199 airtime and no data.