Unfortunately, we have no control over the number of clients that contact you, as this depends on a huge number of variables, including the quality and lay-out of your site, the price and features of the product or service you're offering. However, we can suggest the following:
Think about changing the content of the ad to make it match your offer more closely;
select the most appropriate keywords and add the relevant minus-words to your keywords;
Double check that the link in your ad leads to the main page of your offer. If the link leads users to the main page of your site, it's possible that they won't be able to find your promotion, and leave;
specify the display region, as it's possible that you may be operating in a different region than the people coming to your site
Add time targeting, to ensure that you are available to take calls when your ad is displayed;
Maybe it's also worth increasing your bids for keyword phrases, or turn on autobudget, in order to maximize the number of clicks on your ads and therefore increase the chances of a potential client getting in touch with you.