Who I have the same questioned this topic

According to what I saw online, before purchase, "All 4G devices are compatible with this network extender."  I did not see that it ONLY works for Verizon.  So, I bought one...  Works great for iPhone and Android on Verizon service.  Tried Androids using Sprint and AT&T and those will not connect.  I chatted with sales and they verified that it works with other carriers...  which ones?  unknown...

Does this ONLY work for Verizon cell service?