Pop-up form conneted to piwki


I’ve got problem to solve. We got pop-up contact form on our site. I also got conntected there PIWIK but I don’t know how to connect the data from PIWIK with the data from the form. To match the record from pop-up with the record on PIWIK database about the user who filled form and was on my page before many times.

As example:
Someone was on my site many times before, what is saved in PIWIK db but after weeks of looking for something to buy, he decide to fill and send me the pop-up with contact form. I’d like now to connect the record from PIWIK db to the contact data that he had sent to me so that our call center can call him and they will know more or less what he is interested in by his history.