In a situation where a customer is directly contacting your team in the field to get the updates, as a PM what you will do to control it?

You can politely informing your team that it will cause confusion and create problems in business if in case there is no one point contact i.e officially assigned responsible person (PM) who is the liaison officer between the client and company with regard to the business. And same may be tactically inform the client by providing the required information of contact person/official liaison officer(PM) to have the update from the responsible person. 

It is important to make sure that their is a well established communication protocol 

Most clients would act like this because they would believe if they talk to the team on the ground they would probably get the real time answers they are looking for or directly influence turn around times.The best way to work on this is ask the team members to redirect all concerns to the project manager.This way we stay on top of our game.The team stays focused to deliver better and the client gets guided on the best procedure to follow.

Establish communication protocols/ Communication plan and share it with the Team/ Client. However if the query is minuscule or does not impact scope, time, cost of project- could be answered by team to reduce bureaucracy.

We return to the low as a contract items :- If he has this role to contact directly with your team members then you must let him doing that , but i think that we (as PMs ) must create a balance case between the costumers and our staff because when the company and management consistently side with customers instead of with employees, it sends a clear message that:

• Employees are not valued
• That treating employees fairly is not important
• That employees have no right to respect from customers
• That employees have to put up with everything from customers

My team should follow the communication protocol any individual action will be considered wrong 

My team members answer to me and I make sure they know the consequences of answering to anyone else without my consent.

Their answer binds the team and the company so they have to be wise when answering to anyone else other than me.

This is the protocol: stay sharp and aware!

Apparently there is a trust issue if the assigned PM is not contacted !!! PM should force the communication plan and specify which information is confidential and create an official channel to discuss updates with the client . 

Set up specific discussion periodicity with the customer maybe twice or thrice a week so that they can speak at length with whole of the team and everything is under your control

The customer or client has doubt in actual report submitted to them and does not believe the report and that i the reason why they are contacting to team at filed. To stop this, the report shall include proof / evidence of all status which are mentioned in report. The evidence could be photos with time stamp or video. The report shall reach in time or before due date, so that they will not contact field team. Build the trust wit customer and client.