We support SMS for Pennytel on both Acrobits Softphone and Groundwire. But we do have a couple of notes for Pennytel users.
When we first implemented SMS for Pennytel, it only worked if you had the domain pennytel.com. This is a problem since VoIP calls will not work properly unless you use the domain sip.pennytel.com. This will be resolved in the next update to Acrobits Softphone and Groundwire. In the meantime, users can do the following.
Create a separate pennytel account in Acrobits Softphone just for SMS (give it some Title like pennytel SMS so you can tell the difference). Leave the domain for the account you just use for VoIP calls as sip.pennytel.com. In the new account for SMS, configure the domain as pennytel.com. Leave all other settings (username, password, etc.) the same. After the next update, you will be able to use just the original pennytel account for both VoIP and SMS.
Also, according to the Pennytel API for this, you should be able to set your caller id for the SMS by specifying it in the PennyTel User Portal login under Profile > My Mobile Number. The Number must be first verified under Profile > My Numbers (The Number must be first verified under Profile > My Numbers). This does not appear to work with the API as described (you can see their open API at the link below if you like, the entry for SendSMS is the one we are referring to in this document), the person receiving the SMS will generally just see pennytel as the caller id. We contacted pennytel and they gave us a solution so this should work properly after the next update to Acrobits Softphone and Groundwire.