Give the job to someone else and you, as owner, should then review it. This job should never belong to the owner- it belongs to the person who is responsible for the growth of your company. I believe in a sales department, not a salesperson. Salespeople are NOT expenses. Sales people are self funding revenue generators.
Time is the key here.
Time gives you numbers. If you are an owner making sales calls, it's not likely you will have time to make call-backs. A single salesperson will probably make three to five call-backs. A department with a sales manager will make a lot more call-backs. It's a numbers game.