Bad Service

On May this year I took a WIFI router contract with MTN, and my subscription was 20 gig day time data and 20 gig night time date for R 239,00 per month. My problem is that MTN is only gives me a 5 gig day time data and 5 gig night time data, and I tried all channels to escalate my problem with MTN but so far I get no help and my still pay for it contract. I also tried to cancel it, and I tried to migrate to a big contract. Hello Peter please help me with my problem. The router sim number is ***. Thanks.