Can a house have 2 internet service providers?

AT&T used to be the only ISP in my neighborhood. Had them for basically 10 years and have had nothing but problems. Recently Xfinity expanded here and I want them but am still under contract for 2 years with AT&T. I don't care about having to pay for both I just need faster internet for myself. We're paying for 18Mbps but when i do connection test it only goes up to 9mbps max and 1.2mbps upload. We have 3 phones, 2 ipads, 1 tablet, 1 desktop computer, 2 laptop computers, ps3 & ps4, 1 smart tv, smart dvd player, and a printer all connected to the internet. It worked fine the 1st week but since then its been crap. I want to get Xfinity to use with just my phone, ipad, ps3+4 and laptop and printer and everyone can use there stuff with AT&T. Is this possible? Or do i have to wait out the 2 years?

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