2000 DAEWOO LEGANZA User Comment / Complaint

I received a letter from daewoo motor america detailing corrective action on the cam shaft position sensor in my leganza. i provided them with the required letter affirming that i am the owner of the vehicle, a copy of the receipt showing that the replacement had already been done prior to the letter , and the address to which my refund should be sent. that was last november 2004. i have yet to see my refund, and it is march 23.2005. who do i contact to follow this through? there is no number in the letter for follow-up procedures. i believe they've had plenty of time to respond.