Just to let you know . Att is using three band ca 15 mhz in band 2 10 mhz in band 30 and 5 mhz in band 12, in some parts they use 10 mhz of band 4 .Claro started using 3ca with two channels of 10 mhz in band 66 and 10 mhz in band 12 these days , they were just 10 mhz of band 4 until now.T mobile was using just 20 mhz in band 4 now with 5mhz in band 2 added and Sprint as you know uses ca where they have band 41, 5 mhz in band 25 in most parts and band 13 Openmobile coverage
Which device are you using? Other users have reported issued with non-Sprint branded devices not connecting to LTE roaming. In the last couple weeks I was able to connect to USCC LTE roaming with my LG G7 and data was just fine.