SMPP is strictly for SMS, and you need a direct connect to the network's
SMSC to use it.

This sudden interest in SMPP is puzzling. Several times over the life of
FreeSwitch I've offered to resurrect a SMPP platform that was heavily
used about 12 to 15 years ago, and make it open source. That platform
has SGIP and a couple of other protocols, too. I've never had enough
positive response to make me go ahead with the work.

Regards,
Steve