MTN false advertising on sms then lose all data

This morning I bought 20gb data after I recharged. The sms I received from Mtn confirmed the data is loaded but another sms was received saying I can subcribe to another service, which I wanted because I make alot of phone calls and 85% discount on calls would save me alot of money but no warning was given that I will lose all my data or on SDD code no warning was given that if you change you will lose all data

I literally paid for 20gb data for 30sec and apparently im on a plan I never heard of and I cant switch back