Sears, inc. Keeping my lawn mower Winter Park, FL Nationwide

I bought a Craftsman lawn mower from a Sears Home Store on 7/27/2015. It stopped working on the 3rd mowing. I was tols by the Sears store manager that it was still under warantee so I brought it in to be sent for repair. Then I received a phone call that it would cost $103.15 + tax for Sears to repare it. I said just send it back but they said I would have to pay &50.00 + tax "diagnostic fee" to get it back. I refused to pay it and they have been holding my lawn mower for 8 weeks. This is a vey bad bait and switch business practice which Sears should correct and they should wave any "diagnostic fee" and send my mower back the the Shelby, NC Sears Store without charge.