SIM and WiFi in Denver USA

I used MOSTSIM (AT&T ver.) with Xiaomi Mi A1.
https://www.amazon.de/dp/B079S2SWMX/ref=cm_sw_em_r_mt_dp_U_dTO3DbH4JNTK4

Unfortunately, I only could catch 3G, even Band 5 is in the list of AT&T bands, A1 accepts.

Instead, Diners App enables me to use public wifi, called xfinitywifi.
The airbnb accommodation did not have wifi, but I could catch it in the room. It was very helpful.