Unreliable internet after upgrade to 50/10

Recently upgraded internet service to Broadband 50/10 since ditching U-Verse  and moving to internet TV. Since the upgrade happened with the new wi-fi hardware I get lousy wi-fi coverage throughout my house, even when I'm not streaming TV. I ran a speed test today through the AT&T website which showed 30 mbps d/l which is much less than the 50 promised, even within the range promised. Barely better than what I had before and certainly not worth the price increase. Now even my internet TV service is having network issues and kicking me off. I appreciate assistance in getting this resolved asap before I ditch ATT altogether.