Can only add monthly balance to MR5200 for data usage

I have a 24 month plan data card, but the MR5200 only shows you monthly consumption, not the gross balance. i.e if rembered on the last day of the month, I would have to jot down by balance and add it up! 

I can recieve texts from Three.co.uk and I can text message mr MR5200, but I cannot send a text from it. i.e. text a number to three.co.uk to ping a balance. I also seem screwed for logging into Three as a user, as they seem to recognise non contracted customers. If I try and register with the app, I just a loop of despair. Will try and speak to a human there tomorrow.

If the MR5200 simply kept a cumlative balance, all this would be easy 😞