Poor customer service for MTN

I recharge MTN 50 last Wednesday I was having a balance of 24 before recharge 50 than Saturday I Recharge 26 plus 100 I wanted to buy 1000GB now my balance is 141 I called MTN customers service they gave me MTN email they said I must send them my slips which I did after the said I bought data on 29 -11 how come coz last month I bought 1000GB MTN sim I'm using it only in my router my phone is using vodacom n telkom, this is not fair poor customer service the number I bought airtime *** this is how MTN treat customers *** ***