Anyone understands GSM really well?

[telovoy]

Hi guys.
I am in a situation where i don't know where else to go for this problem i have, so maybe there is some people here that understand the GSM system really well and can point me in the right direction to find a solution.

So this is the deal: I switched my cellphone provider to a GSM company. To be more precise, i switched (ported my number) from CDMA boost mobile (a Sprint mvno in the US) to gsm Red Pocket (an AT&T mvno).

So my probem is that these MVNO companies suck at having any kind of decent technical support, and i am having the bad luck of not be able to receive any SMS since i made the switch 5 days ago.

I can actually send SMS to anyone and it works. The other party does receive my messages. But i can NOT receive messages back, EXCEPT if the other party is on the same network (AT&T)

I spent many hours on the phone and chat rooms with the Red pocket wanna be tech support guys, but they are not able or willing to resolve the problem. May be they don't even have control or the ability to do anything at all that's why i would like anyone here with the knowledge to explain a bit where the problem could be.

Here are some pointers to help with the troubleshooting:

1. I got a brand new original SIM card, and being told it was the cause of the problem because it was probably a bad one, i got ANOTHER one, called red pocket to transfer the line to the new SIM, but this did not fix the problem.

2. Had them "reset" the SMS system on my line twice, same result. (i dont even know if that is some BS they pulled to make me hang up while rebooting the phone)

3. Device: I have an iphone 4. It is locked to AT&T, but since red pocket its actually the same network, it works anyway, and i have it configured with their settings so everything should be good.
Yet, i have another Iphone 4S, same thing, and even more, i have a 3rd device, an unlocked Blackberry, which does not make my line to receive any text messages, so i believe the bad device posibility, its not an option here.

4. there is a special command they gave me, that shows you on screen the number of the gateway the phone is using to send the SMS's and it is on the right setting.

5. I called the previous company, to make sure there is nothing left behind, like an incomplete port to the new carrier, and they confirmed that the system shows the transfer being completely made and that there shouldn't be any issues.
My thoughts at some point were that it might be something like when for example, a domain name takes some time to propagate on the DNS servers until it works, maybe SMS system work kind of so like that, but 5 days already, i don't think so.

Then... you might suggest to just switch carriers and try again, but i really need to be on the ATT network, because it is the only one with enough signal to be able placing calls in my building... all the rest fail. And finally, the oficial ATT is just DOUBLE as expensive for exactly the same plan as Red Pocket does.

So do you know where the problem could be?
The tech support guys are probably in Pakistan, following a basic manual with a set of instructions, but it is taking them and me as far as just hanging up the phone or closing the chat window when they don't find any solution to my problem.

Sorry for the long post.
Thanks for any help and tips.
Good luck