Poor service for wifi equipment

Well today I called to complain about my internet I x5 gb speed but my wifi modem is a wifi boost 6 that only is good for 2.5 gb I need the new wifi modem that is wifi boost 7 that is good for 5gb speed I spent 3 hours on the phone and when they finally told me they would send a new one out I was told I would have to pay $200 for it I already pay $300 a month for my service all I want is a wifi modem that works with my plan