Mixing of calls personal and official airtel numbers - weird case

Believe my guys i am not on drugs but this is what occasionally is happening with me. I am working in my company since past 9 years and off late from 1-2 years occasionally i keep getting official calls on my personal airtel mobile numbers and when i pick up and reprimand the person and scold them from where they got my personal number they swear and say that they called on my official number only. Some facts below: Official airtel is a postpaid connection in company's name - device iphone Personal Airtel is prepaid connection in my personal name - device motorola Both phones are always together, and when i check call forward status on official phone everything shows deactivated. I am totally clueless as to what exactly is happening and why the official calls are getting jumped to my personal number occasionally.