I upgraded my Nokia 7.1’s 12-month mobile plan to a lesser amount because I’d never use the 80 GB allowance plus if I had renewed at the same level, the unused 50.6 GB component from the previous year would have rolled over.
The plan has two sections, a Pay-as-you-go base plan that costs a minimum of $15 p.a. & the added data & unlimited calls/SMS/MMS portion.
The PAYG credit is used to cover international calls & video/audio files sent via MMS. I discovered another use for the PAYG credit: it can be used to offset the price of the $99 0r $249 Super Special 365 day plan.
I had in the normal course of events, accumulated $40 in PAYG credit so I chose to apply $30 to the $99/12 GB annual plan. So I paid $69 instead of $99 & off-loded excess PAYG credit.

When the 12 GB runs out I can add a $50 data allowance of 20 GB which may be all I’d need for the rest of the year, based on previous usage.