Texts Diverting

I have a problem.

I have two phones on Smarty, during the working day I have my main phone set to divert all calls to the other number.

Since the 6th March all of my texts also divert to the other phone regardless of whether the divert is set or not.

This isn't an option that's even available in Android and if I check divert status it tells me that SMS is not diverted.

I'm at my wit's end trying to cancel whatever has happened.

It makes receiving verification texts very awkward unless I've got both phones open in front of me.