Confusement over Billing -£16

[Naomirosec_]

I upgraded my phone on 28th May (my usual billing date) to the iPhone 11 Pro Max.
My airtime plan is £35.00 and my device plan is £51.22.
I also used my NHS discount but was told that most likely won’t start until next month.

However I’ve come to pay my bills today and was only able to pay my device plan £51.22. When I went to pay my airtime plan, it said it was already paid and was -£16 (which of course it would said it’s already paid if it’s in minus)
I’m just really confused as to why it was -£16 and not £35.

Thank you!

[MI5 · Accepted solution]

@Naomirosec_ 

The only way is if your new airtime tariff is cheaper than your old one. 

You would have paid already for your old tariff (a month in advance) so you would be in credit if new tariff was cheaper.

[Naomirosec_]

Ahh that would make sense, thank you!

I’m not sure if it was cheaper as with my old phone I paid the bill as a whole, rather than it being split between airtime and device! So I’m not too sure, because as a whole my bill for this phone is more expensive. So I’m not sure which had the cheaper airtime plan!

But this would make sense though. Thank you!

[MI5]

@Naomirosec_ 

That would explain it as you are now on refresh rather than a standard tariff so your bills are split.