Back in the dark ages there was a time where internet connection providers charged for time online. Not amount of data. At the pre-historic modem speeds you wouldn't get much data anyway. So you got the 100 hour plan or whatever you thought your needs were. Now you've paid for 100 hours of time online. If you didn't use it all then the unused time would be banked and you'd have 127 hours (or whatever) to use for the next month after renewal.
This is how it should work. We paid for it. We pay for it again. It should accumulate. Be banked. Rollover. Whatever you want to call it...it's ours.
But no. The telco's found out/were permitted to that hey they could charge per month and take away what you paid for. Profit city. This is part of why I so like the add-on method of use. I pay for it and it stays on until used. It's why I picked up the 5gb/SIM promo last year. It's an add-on. With the summer and Dec gifts I still have 4gb of that left. I'll of course admit that I'm a low use customer. When I last examined my usage 3 years ago I was averaging about 400mb per month on the actual phone. I had a 6gb plan but it was otherwise being used for the hotspot. I think there was only one time that I used it all.
So here we are. We can wish all we want but the telco's won't do it unless they're told. Tell your MP. Tell the Prime Minister.
