Billing, tier and credit questions

I am really confused about this subject.
I bought land and prompty sold it but tier says its still at maxium level.
Will it remain this way for this month?
Also how do I prepay for land tier, month dues?
I read something about their is way to credit this.
Will it take money out of credit account monthly even if I prepay?
Why do I have to use paypal to repay or use the "credit"?
Am I missing something is credit relating to what Lindens I have earned or what I have prepaid?
Also is there way to change my month to month billing date?

Hi FD,

Yes, your tier reflects the greatest amount of land owned during a billing period, so even if you own land for a short time, you will be billed for it.

You can pre-pay Quarterly or Yearly for your premium account which is cheaper and cheaper still. This is just for the premium and it's associated 512m of land. Additional tier charges still apply and can't be pre-paid. You CAN put a balance on your account, but it will be used for any purchases you make, including L$ from LindeX.

Credit refers to what you have pre-paid, and/or what you have cashed out (L$ to US$) using LindeX.

And I'm afriad it's not possible to change your billing date, sorry!