tv/internet to just internet

i have the package deal of tv and internet for 79.99/month, i do not have a cable box and opt out to have one on purpose, been with the plan for a while and i dont even use the service to watch xfinity tv online, i have plenty of other means to do so. i would like to just have internet, i am supposed to recieve up to 100+Mbs download speeds, i see a plan for 69.99/month called "Blast!" and the speeds are up to 300Mbs and thats at a No Term Agreement plan. its in my area  but everytime i put in my own address and see to change my plan the opportunity is neglecting me to do so, i want to change my no use of tv plan to a more cost effective and faster internet connection plan