DATA EXPIRE IN ONE WEEK. 3rd Bundle that just expires

I have bought a 100mb bundle and for some reason on the second or third day my bundle is suddenly depleted. I know how these phones work , and I have deleted the google services for chowing the data, Now what I have is general apps like whatsapp and the internet. How come when I put data on my phone, no later than two days it disappears. Totally unacceptable, I cannot keep buying data which I do not use and it just expires. I HAVE PAID FOR THAT DATA, you keep taking from me!!!!!!!!!!!!! It cannot simply expires when not using it, that's the whole point of saving. This is my 3rd 100Mb data bundle that just expires. Cannot believe MTN is willing to take our data which we paid for if we don't use it in 1 week. RIDICULOUS...