They’re domain hijackers! If you’ve found this blog post, you likely already received an email from registerservicedomains.com warning you to hurry up and renew your domain name(s). Funny thing is, they are not your domain name registrar. Do not renew with them, do not give them any money, simply ignore them and delete the email.
Best advice:
If you have a website designer, ask him/her anything you need to know about your domain names, don’t trust the random emails from people like registerservicedomains.com.
If you don’t have a website designer, just goto http://www.whois.sc/. Type in your domain name and click “lookup”. The following page will reveal your true administrative and technical contacts.
Website Survival Guide 
It seems that you have a great expereince with their services, anyway I will take care of not to follow any of their services.
China appears to be the origin of most of these domain hijacking scams, or at least the “sender” appears/claims to be from China.