Will the potential new employer call my old job?

I'm afraid my potential new employer will call my old job. I feel like I have no chance of getting a new job, even though I had three very good interviews that ultimately ended in failure. My qualifications and grades shouldn't be a problem. This is very frustrating, as salespeople are in high demand everywhere. Unfortunately, I didn't part ways with my old employer on good terms. So I'm wondering if the new employers are calling them?

Thank you in advance for answers