MTN *****ing data I paid for

Why am I allowed to add a 1Gb top up of data for my daughter yet it has an expiry date of 1 month from the date I purchase the bundle. I can understand the free 1Gb given at the time of purchasing the bundle has a month expiry date but if i have paid for the 1Gb bundle I should be able to use it as and when i want to use it without being ****** back by MTN, this is surely considerd theft and bad business pratcice to increase sales?<br> This is costing a fortune as she is at varsity where there is WIFi but uses the data when out of wifi range which is very seldom as we have wifi at home as well, In the past 1Gb data used to last 3 months... so what and why has it changed WITHOUT NOTICE<br> <br> Selwyn