This company scans domain records (whois information) and sends a renewal notice via the US Mail about a month before the domain expires. The company tells you you need to renew your domain registration and charges three to four times for the registration. If you send them the money they then attempt to transfer the domain from your current registrant, which will very likely take down your website when the dns entry is moved. If you look at the small print of these letters, somewhere on the letter it will tell you it is an advertisement. Contact your current provider BEFORE you send them money.
A church we are hosting paid for the domain renewal through this company, I found out when I started receiving emails stating the domain was locked and they couldn't transfer the domain.