We've been using IC Systems and Adams, Cooper & Marks for several years and they aren't terribly effective, but then there isn't much they can do.
They can call, send letters, and threaten, and then report the balance to a credit agency, but unless the company wants to take the debtor to court, not much else can be done.
There are a number of things the customer can do to avoid collections for legitimately owed balances, such as:
* Dispute the charges, muddies the water and causes the agency to have to review every cent of the charges with us.
* Insist they never received an invoice or anything notifying them that they owed the money.
* Tell the collection agency they won't accept further contact from them-they are legally bound not to further contact them, but few people know this little trick
We ended up going to advance billing to cut down on the problem.