Ver very slow wifi speeds

I phoned rain support this morning about my internet being very very slow between 5pm and about 12am when im actually watching series or movies online.the guy gave me a ref number and said someone will get in touch with me today still and guess wbat? I am still waiting.im on the rain ine 30Mbps package and during the the i get speeds up to 28-35 mbps on average which very good for my needs the problem is im at work between 8 and 5pm so no one uses the wifi.please fix this before i rather cancel completely and i dont want to.evenings i cant stream at all im getting between 2-3 mbps speeds and with the lowest video qulity of 360p and its still buffering