Matthaeis Camco, Inc aka SABILITY INC send me a check $3,350 check prize check asked me to return $1,950 for taxes Sweet Home,, Oregon

I received a check today 7/5/12 telling me that I am one of the winners for all customers of Wal-Mart, Sears, Home Depot, Safeway ASDA.  That I am entitled to $50,000.00, however a check for $3,350 was enclosed that I am to cash and return $1,950 for non-British taxes by Western Union.  The check is drawn on Wells Fargo from a company called "Matthaeis Camco, Inc." but the letter is from a company called "Sability Inc. from Duluth, Georgia".  The letter also tells me not to cash the check without calling a certain number (1-505-652-4778) first. 

This letter sends up so many "red flags"  It is signature on the letter is not the same as the name typed on it.  I shopped at Sears earlier this year and didn't registered for any contest so why was my information selected/entered.  I don't shop as any of the other stores, this concerns me that my information was given/sold/purchased/stolen by these individuals.  Not only that, if I am a winner, why should I be paying taxes overseas when I should be paying local (American) taxes and why didn't this check come via certified mail with a return address on the envelope?  Why two different company's names?  Why not explain how I was selected? I am sure I can think of a few more questions that need to be approached.