United Recovery Systems (URS) is a legitimate collection agency, but some of their offices/reps are too aggressive. Here's their phone numbers and addresses:
https://www.unitedrecoverysystems.com/home/contact/

(If they use unfair collection tactics, submit a complaint to the BBB and they'll mediate).
See others complaints at http://www.bbb.org/houston/business-reviews/collection-agencies/united-recovery-systems-lp-in-houston-tx-16800/complaints#breakdown

(If their collectors use illegal practices, go beyond the BBB - there are fair collection practices that apply to all agencies.)
The government FTC website has an easy-to-understand page explaining what a Collection Agency cannot do:
http://www.consumer.ftc.gov/articles/0149-debt-collection
and includes where to file complaints at the bottom of that page.