i went to petronas on 2nd september. initially inserted maybank debit card, and it 'failed' shown on the screen. according to the petronas people, the line is not stable that day. so i ended up paying cash for petrol.

to my surprise, today i've checked up my debit card history.
02-Sep-2009 PREAUTH SALE PETRONAS, DEBIT DATED 02/09/09 RM150.00 .

the question is:
1) i don't make any purchase using the debit card. attempt is made but failed show on the screen. so i used cash in the end.
2) why does it credit rm150 from my account? and until today, i have receive the refund.

what should i do? any1 has the same problem before? HELP