Do you have what we call an adsl broadband connection.
Or are you on a fiber optic based broadband service.
If it is the first of the two get your phone line tested from your house to the local exchange. If it is the problem then no amount of changing your ISP will solve your problem since it will be down to the quality, or state of the phone line.
It is the same for a fiber optic broadband connection, only more can be done.
If there is too much noise on the line or the power is too low or high it will cause loss of service or intermittent drop out of the service.
So call the fiber optic cable company and have an engineer test the power, and noise levels of the line from your house to the fiber optic box at the end of your street.