Consistency of contact information (local phone number, business address
& email address) is the key to claiming and merging separate Google
Places Pages. Ensure that you have this contact information included
somewhere on your site as well, and check to make sure that it appears
as crawlable text.
If you are trying to claim a very content rich Places page, Google ads in an additional identity confirmation hoop for you to jump through: the phone number listed on your sites WHOIS page.
In short, the equation for claiming Places pages is:
Website address + crawlable phone number on contact us page = mailing address submitted to places page + phone number you submit to places = your actual phone number & mailing address at the business = the phone number that appears in your WHOIS website profile. Mind the email you use as well.