I am amazed as to how those who submitted to Mishre Directory could do so without knowing that it is a paid directory. I even stated it clearly in the guidelines! What should I do?
See if the submissions are coming from one specific source. Its possibily some form of automated submission software... although ultimately your captcha should stop it. Alternatively it might be that people are getting to the payment stage and didnt initially realise that payment is only via paypal.
I get this everyday. I think people are just trying to get in without paying or are using automated software. its the life of a directory owner I guess!
There could be several reasons, apart from spam (although that can happen). Check out this thread: http://forums.digitalpoint.com/showthread.php?t=391555
Captcha wont work, IMO you can try an0n's spamguard. It blocks almost 110% of spam submissions. So no more worries.
It could happen that your directory got listen in some "Semi-Automated" software and now being target of such submissions. I got three such submission few days ago, I even sent them mail asking about it and so far no response. Thats what I hate about it. They don't even have courage to reply. (One of them is even a DP member)
Also worth checking everything is ok for going onto the stage of making payment, making sure that everything is working is worth checking.