With Scrum implementation, you will have a set of Stories with associated tasks to complete within a fixed time frame of approx. 2-3 weeks. Now, if anything new comes that ifarises for the team has to work on it should be prioritised for the next Sprint (ifassuming it couldcan wait for this time). Else,Otherwise someone has to takemake a priority call on it and whether the team should work on this withthe new piece within the current stories. A stakeholder (PM) could removemove a lesslessor priority story for next Sprint, if that is possible. Else,Otherwise all the stories should be completed within decidedagreed time frame.
Else,Alternatively you could haveset a Support process up between DEVDevelopment and the Customers (in they are not thousands of them). Allocate, and allocate some of teamsthe team's time to it and then work on these tasks in parallel with the assigned planned Sprint Stories.