Web pages will not load through Safari on all my computers using my AT
I am using Safari 8.0.5 and OS 10.10.13. The last couple days when using Safari through all my computers using my AT&T internet connection, web pages either will not load or they load very slowly. Safari will indicate it cannot find the site. If I run Safari, using all the same computers, through my Verizon MiFi Connection, it works fine. U-Verse works fine. Mail works fine through AT&T. I am able to use Internet Explorer through my AT&T connection on a work lap top without difficulty. I have deleted caches in Safari and deleted history in Safari. I have contacted AT&T and they do not know what is the problem. When I check my download and upload speeds for the internet using Safari and the AT&T connection, they are slow. When I do the same using the Verizon connection, they are fine. Does anyone have any ideas? Thank you.