As others have said you will incur interest from Day 1 if you use it directly to get cash to pay off your O/D. This will cost more than your O/D.
So here's how you do it:
You cane the arse off it and buy everything you normally buy for cash with it - groceries, petrol, etc. This allows you to dent your overdraft. FFS don't go on a spending spree. Then with the money you have saved from not being caned by your bank, you note the date at which it must be repaid before you get interest charges and you clear it. Job done.
If you lack the will to pay it off IN FULL before they hammer you for interest, or you lack the will to not go on a spending spree, cut the bloody thing up now.