Incompatible device issue

We switched to Xfinity mobile.  During this process Xfinity agents told us our Samsung A21 was compatible with their network.  So, we switched an A13 Samsung first to make we had service in our rural area.  Then we went switch the A21 and then were told it was incompatible.  Anyone else rely on agents statements for compatibility only to find out later that your phone was incompatible?  This could be just a mistake or wondering if it is symptomatic of an Xfinity policy?  We spent hours switching and getting some resolution.  I will give Xfinity some credit for trying to work thru our issue.  But it took some persistence to get to someone who could resolve our problems.