Unstable internet

Have a 20gig 4 mgb internet and adsl line from Telkom. During August line throttled reached limit. Purchased extra 20gig. Line still throttled/unstable. Reported to call centre problem not resolved. Telkom called ask if problem resolved told them no. New month September new 20gig but internet still unstable. Logged a fault via telkom app. ***. Should this not get resolved this time I will cancel and go to openweb