Company asking to pay employment cost

Before I resign I made sure that I've completed my bond contract with this company. I filled my clearance from them last August 2011 and till now November 2011 I haven't heard from them for my back pay and Certificate om employment. All I got from them is a letter several of them asking me to pay at first 7,000 php, because they think that they gave me too much salary, the last letter they sent me, they are now asking me to pay 45,000 php! I don't know how they came up with that amount they even threatened me that they will sue me if I didn't pay the amount. Additional information, their payroll is a mess, for more than a year they been giving us incorrect salary, to make an appeasement they gave all of their employees 10,000 and said will deduct it in our salary once they have corrected their payroll. Please help, I'm unemployed and emotionally distressed by these problems.

why are you being charged 45,000? did they provide proof of what they are claiming?

I don't know where the 45,000 came from. They were just asking me to pay it and didn't even provided me any breakdown. They just said that there was a miss calculation of my salary, I was over paid and they want the money back. The truth is I was under paid most of the time! And if I owe them money from the 10,000 appeasement salary that they gave me, it would be just around 2,000.

then you can write back and state that you do not believe you are liable to them for anything