Is Yodle located in California as well?
Its difficult to assure you that it would be an easy claim. You would have to establish the lost business, which can be difficult. That being said, that you know how many hits you had in comparison to the amount of calls is good evidence. Along with an expert witness in marketing and accounting who has knowledge of your market, this could be turned into a damage claim.
However, getting them to restore your number is XXXXX less likely if you don't have an agreement in place with them to list your number.
That doesn't give them the right to mislist your number and divert customers, which is what they are doing. They should have simply taken your listing down, not misrepresented your number to potential customers.
Lets assume that out of every 400 people who saw the advertisement, you get 20 customers. Would the net profit you make from 20 customers justify paying a lawyer to go make the claim for you, or having to pay litigation expenses, hire an accountant to come put the damage model into place? This is the kind of money you would be able to recover.
If its, worth it, then lets talk about what you need to to do to file a suit and if you want to get a lawyer.
If not, then you should send a stern letter to them telling them to remove the false number altogether and threaten legal action if they don't. You can defintely get a court order for them to take the false number down. If that is the avenue you want to pursue, you need to file a suit against them requesting an injuction.