Problem while configurating SIP

Hello Everyone!

I just joined the forum after getting my first OBi100. I'm currently having some issues while trying to configure my SIP on it, but first I want to give you a little of background:

I'm residing in Mexico and my provider is from Mexico, it's in fact Axtel (for those who know) and they provide land line together with VoIP. I've successfully configured my VoIP account in several devices and software but now, with the OBi100 I'm getting the following error:

"403 Registration to foreign domain are forbidden"

I've tried configuring from ObiTalk page, ObiExpert and Device gateway page (I went trough all documentation in order to do this) but the result is the same....

Does anyone know what this error means or if it's related to my provider only or a bad configuration?

Thanks in advance.