speaking by experience, you should make your service more exclusive. When you talk to clients over the phone, show them the value, ask questions they have to answer yes, and don't be afraid to really push buttons on the closing. If you don't close on the first try, go over some of your sales arguments again, try to close again. Always remember that with most business owners if they are still on the phone, the are somehow interested in what you offer.
Now to the part of making it more exclusive. When clients ask me to send email or if it is possible to meet up just write down some pre made answer like this:
I am sorry sir, for packages at this price point we simply do not meet with clients.
or We are an internet company, and therefor naturally our business only do business through email/phone.
or little more grey, but it works depending on your country's laws and legal system.
or since we only offer this to x restuarants in x city, all business owners that understand what this is and how it this service. So either it could be you, or the restaurant across the street.
If they ask you to email the offer, this is usually a nice way to say NO!.
if they ask for email with the offer, say that you will send him the confirmation of the deal with all the details, but no offer.