8 port GSM Modem problems?

Heya guys, wanted to ask few questions about sending sms (marketing) using gsm modems. I've got one 8 port gsm modem up & running, wrote a software runs smoothly sms are being sent, received etc etc. The problem im facing is that im using AT&T sim cards and today (it was the first sending done) they blocked the sim cards (account suspended). went to store they have no clue what happened but i assume its the bulk sending.

Can anyone share any similar experience and/or provide a solution like using different carrier and which ones ? im talking for sending of about 20-40K per day strictly in USA.

 

I'm sure they are making it tougher and tougher to do with filters. Theres no real way for the receiver to report sms spam, so it must be the content of your message or the number you are sending per sim.

 

I have the same problem

 

I've ran into the same issue several times. It seems to me that the carrier is blocking simply due to the bulk amount of messages being sent. Haven't found a solution just yet but I do recommend staying away from major carriers (AT&T, Tmobile, Verizon) as they are usually more strict with their "unlimited" messaging plans.

 

Anyone want to sell their 8 port GSM program?