Slow internet speed from Mweb, NOT their fault they say......

For 1 year I have a slow connection speed, I cancelled today. Now a tech phoned and whilst everything is off the wifi, and the speed still slow, 2Mbps, he raised his voice and tell me it's my fault. I am over this slow internet with mweb. Worst service I received in my whole life! For 1 year I must keep on paying for 4 Mbps, but receive between 1-2mbps