[I have bought $L6000 but they do not appear to have been credited to me altho my card has been debit]

I just talked to billing and there is account maintenance going on.  secondlife.com/status.  I was advised to check back after this finishes and the account should be credited at that time.

 

[Bought Linden Dollars and they have not shown up??]

Same thing happened to me.  In my account it shows the transaction was successful but the money has not come into my SL account.  Also, two purchases have not been delivered, although the payment has been sent.