This all sounds like it could do with a little clarification with what goes on with Subscriptions. We can’t discuss specific payments or purchases, but a general overview should help highlight what’s going on.
Basically, when you set up a Subscription, if you don’t already have time on your account then a couple of days are added to your account up front in good faith that it’ll go through, to allow time for the payment to process, since any digital payment takes a little time. That’s the reason you only see a couple of days at first.
If you do have game time on your account, then you may still see the couple of days pop on temporarily, but the charge then doesn’t actually happen until your existing time runs out. More info on that one can be found here: https://support.blizzard.com/article/000255300
If the payment clears, which generally is done within 24 hours, then it bumps up to the full amount of time you’ve purchased. If not, then your account freezes and your Subscription’s cancelled.
You can keep an eye on the progress of any purchases over on your Transaction History here: https://account.battle.net/transactions