Employees want to use their mobiles more and more, and want to use them anytime, anywhere, anyplace. As an employer you want to help them do that because it's an employee satisfaction process and you know it makes them more productive as well.
The problem on the flip side... is you will lose brand recognition and brand identity, in that if they make a call from their mobile, the call is going out from their personal mobile number not the long established company number.
The fixed number is more trusted, it sets companies apart from the one-man-band and people tend to trust fixed line numbers as opposed to mobile numbers. A fixed line number implies a physical presence, a longer term entity and a lot of people don't actually trust calls from mobile numbers they don't recognise. Many of these calls go unanswered meaning the caller has to go through the process of leaving a voice message or sending a text message just to try to have a conversation, more wasted productivity.
Adherence to corporate processes or business procedures that you have put in place, are really important to a company, maybe even critical.
So if a customer rings back on an employees personal mobile, they have just bypassed some of the things you have put in place to help your business. For instance there is no record in the companies systems so things like call analytics or call recording are out of sync.
The customer has inadvertently gone around the back and circumvented everything you have put in place and gone directly to an employee.
That implies another problem, in that the employee could be on holiday, have a flat battery or simply not be available to answer calls and the communication experience between customer and company is not as good as it should be and could mean losing business.
Worse still for the business is if the employee leaves, the only direct contact a client has with the company is with the ex-employee, making it way easier for them to steal business away from you on behalf the new company they are now working for.
The solution is simple - allow employees to use their personal mobile phone but give them the ability to call from the companies business numbers. This retains brand recognition, improves efficiency and curtails customers inadvertently circumventing your business processes whilst ensuring the risk of ex-employees stealing your customers is diminished.
We call that a win, win