We've really been struggling with MelissaData's "quality" services. We initially signed up for their monthly service (with auto renew option), when the first month was up they canceled our service without any notice. Placing a call in to the help desk uncovered that it was "an accident". They have reactivated our account, then when the second month was up they simply blocked our IP address so that we absolutely cannot gain access to their data. After calling their support we've been told that it is a source code issue and absolutely has nothing to do with blocked IP address (Yeh Right, I "certainly believe them") and we were also told that ONLY a president of the company can fix this issue. But since he is such a busy guy he of course don't have any free time to be fixing these bugs. That has been going on for passed 3 weeks now without any resolution. So if you need to choose a data company, I would NOT recommended choosing
http://melissadata.com