instantcheckmate I authorized a one-time use, but they turned it into a recurring monthly charge Las Vegas, Nevada

you should read their Terms and Conditions.

Here's part of the Terms and Conditions...

By default, all plans are scheduled to renew automatically when the selected term comes to an end. Customers can cancel at any time by calling our customer support line at 1-866-490-5980.If you selected a trial membership, your five day $1.00 trial (or $0.99 trial) will expire in 5 days. If you would like to cancel before the trial ends, you may do so for any reason and you will not be charged again. Simply call 1-866-490-5980 between 5:00 AM and 7:00 PM, PST, Monday through Friday, or weekends between 5:00 AM and 6:00 PM, PST to speak with one of our Customer Service Representatives. Otherwise, your trial membership will end five days after you signed up, at which time you will be charged the standard monthly rate of either $14.63, $19.63, $24.63, $29.63, $34.63, or $39.63. The monthly rate is determined by the promotion that was running at the date of purchase. Your membership will automatically renew every 30 days thereafter until you cancel.

O-o-o-p-s.

You now need to read all of it and make sure you cancel future billing properly.