Paying for a 4mb line and not even getting 1mb

I recently upgraded my 2mb line to a 4mb line. This is the fastest line available in my area. I also changed from having my line with Telkom to Mweb. Since doing this, my internet connectivity and speed has been **********. This evening when I measured I recorded a whopping 0,62 mb/s download speed, 13ms ping and 0.56 upload speed. This is a regular occurrence and I am forever resetting my router. On the 2nd of February I also measured 1.21 mb/s download speed. This is unacceptable as I am paying for a 4mb line and my problems only started after moving from Telkom to Mweb. If this continues I will have to take my business elsewhere.