shoppers point of sales sweepstakes Shoppers Direct sent a letter that I won money through a purchase i had made las vegas , Nevada

I receieved a letter from shoppers direct that said i had one 50,500.00 USD. It also stated that i won the money from a purchased made that was electronically selectedd and entered for the sweepstakes. Also that my name was attached to the ticket and serial number emerged as one of the winners.

It states I was randomly selected through the computer and confirmed as a winner. The it states that i need to contact their claims agent Don Peterson at 1-647-829-7556 between the ours of 9am to 8pm mon-fri and 9am to 5:30pm sat. 
 
Then that i had to claim the winnings withing 30days from the date of the letter. That if i dont cash it within 30 days that the money would be included in March 2012's drawing. I was given a check for 3,550.00 USD issued to me in the form of a check by Southwest Independent School District through Wells Fargo Bank as a partial payment which was deducted from the total winnings.

Then it states that i must call the agent to activate the enclosed check before deposting it into the bank. It informed me to then call and get the address to send my payment to the appropriate tax agent. Sincerely, Amanda Armstrong.