I tried to use a sim bought from KnowRoaming for U...

I tried to use a sim bought from KnowRoaming for US travel recently, but had all kinds of troubles. I exchanged over 20 emails with their support department, and they told me to changed a bunch of settings. At the end of the day, the data connection continues to be unreliable and unusable. It would be better off to just buy a sim from a US provider, instead of going thru the trouble of using KnowRoaming.