afternoon internet service issues

Why is it that my internet level of service drops drastically after 2PM EDT every day? I have fiber feed to my house for Internet, TV, Home telephone service as well as Cellular service. I have gone through same issues with ATT DSL, Charter broadband. It seems that once a 2 year commitment is fulfilled, the level of service takes a big dump. There is no customer loyalty for customers that stay with a service provider and that really stinks!