Nagios SMS notifications to iPhone Never Come From Same Addr

So I have Nagios setup to email alerts to <my_cell_number>@txt.att.net, which forwards the note as an SMS message to my iPhone. Every single message that comes through via SMS appears to come from a number like “1 (100) 101 900”, with each consecutive message incrementing its from number by one.

For example, say the first SMS notify I get is from “1 (100) 101 900”, the next will be from “1 (100) 101 901” and the next from “1 (100) 101 902”, and so on.

Has anyone else had this same experience with SMS notifications to the iPhone, and more importantly…has anyone found a solution to get them all to appear from the same sender??