Default Unreadable Messages M+ access Code: 7258

Hi Everyone

I'm using a stock Sprin LG G2 and having trouble with my text messages being.. scrambled. For every message, the body just reads "M+ Access code: 7258, Message ID: HTWE5379".

Any idea what this could be or mean? I've tried googling as an LG and as an Android issue but coming up empty. It happened on vacation so I'm not sure if this is due to roaming, but are all the messages I received just lost? That doesn't make sense, even if I'm travelling I should still be able to get messages, whether roaming or when I return.

If I can provide any further details or if you have any thoughts please let me know.

Many thanks in advance.