Mtn lies and daylight *******

Mtn called me and offered me a data package of 80gb day and 80gb night on a sim card only and promised that whatever is not used will carry over to the next month,I'm hardly at home so that would have been more than enough for me..only to find out a few months later that they **** and I have not been receiving that 80 day and night and the data cuts off on the 20th of every month.I want to cancel because they obviously **** ,now they ask me to pay a cancellation fee of R2000,for what???? Because I did not get a phone from them! Only a simcard that does not even give me the data they promised!