I've been getting odd texts lately as well. Lately, when I get a text from someone I get a second text shortly after that contains a lot of gibberish (like when you view asian text on windows without the language pack you see rectangular characters), along with the date & time, and a link that's usually 5 numbers (73.788 for example).
The number it comes from is the same as texts from Verizon (like when you change something on your account) except for the last 4 digits. The ones from Verizon usually end with 4000, where these end with 2020.
This started after I got the Thunderbolt, so I wonder if it has to do with devices that have a SIM card. Anyway, I've got a ticket open & we'll see what happens.