You have to sign into your dell account and cancel from there.  It is an extended warranty that seems to be automatically added to your invoice.  I had the same problem and talked to a tech who showed me what to do.  I still have the basic warranty, which is all I wanted.  If you look on the bottom of your invoice you should see Monthly Subscription Premium Support which will show you the charges that you receive every month.
I recently bought a dell laptop with a laptop case. 3 days later after i paid for both products i have a charge on my credit card of 26 dollars with no explanation. What is this charge? i paid for both laptop and case during a tax free weekend. I use a cash app card loaded with money for all online purchases to avoid fraud, but i now have a -26$ balance.. what is going on?
Unexpected charge from dell dmi sales on my credit card