Title explains it all for the most part, but I am using a EC21 8 port that I bought from Ali. Everything is working fine just after 300 deliveries it stops delivering and I get a bunch of failed sends. Im not good with AT commands or how to use them on windows so please if you could help with if you have a solution.
I am using SMS caster with tmobile 4g LTE for the record.
P.S one of the fixes I was reading suggested depleted call credits, which is not the case these are fresh and full, and another one is incorrect SMSC, but SMS caster is reading “+12063130004” which is the correct once. What could it be?
I would also like to mention that turning off the modem and rearranging the 8 Sim cards, or turning it off and plugging into another USB port fixes the problem. Till I get to around 300-1k deliveries before it gives me CMS 350 problems.