What is the ruling on my conducting sales operations from the the office via telephone, and from my personal mobile phone outside of work hours, provided that the interest of the business is not affected?

A private employee, like a salaried worker, is not permitted to work for anyone other than their employer during working hours, because their services are owned by the employer. Exceptions to this include the five daily prayers and their confirmed Sunnahs, as well as what is customarily excepted, such as meal times and answering the call of nature, or what is explicitly excepted by a condition. If the employee works for someone else, their wages are to be reduced by the amount of time they worked. An employee making personal calls or conducting private transactions during work hours deprives the company of its benefits and causes it harm.