Unethical practices with Dell Tech Concierge

I purchased Dell Tech Concierge for the Third time in January 2015, because I thought it was a good deal, but because I was a few days over the re-registration date, they forced me to pay full price--instead of the returning customers's discount. They took my money willingly, but did not tell me that after one more year, I could no longer purchase Dell Tech Concierge because my computer is now 5 years old. They also ASSURED ME that since I was again paying the full price, that I could purchase the service the next year at the discounted rate!

So, when I recently tried to purchase the service again (Dec. 2015), they told be NO! (BECAUSE MY COMPUTER WAS 5 YEARS OLD). It is quite plain that they should have told me all this back in January of 2015, when they took my money for the current plan. I think it is only fair that I should be given ONE MORE YEAR of the plan, for the DISCOUNT RATE. I am amenable to working with Dell, and Dell Tech Concierge, but I insist that they treat me fairly!