UAT (User Acceptance Testing) is usually done at customer side. The customer checks whether you did what he asked you to do and how well the job is done. If there are comments from the client (usually these are bugs) the tester is required to do the following:
Check to see if you can reproduce the bug. The style of the client may be different from what you are used to seeing in your team. If it does not work out, then you can ask him for more details (browser, User ID, video recording). Keep in mind that work on client bugs is high priority. Therefore, you should postpone work on other features so that to do research on UAT bugs.
If you could reproduce the bug, but in your opinion, this behavior of the system does not contradict the requirements, then send a letter to the client with a link to the place of the specification that confirms your correctness. Perhaps you did not understand him correctly, or the client himself forgot what he was asking for. It happens that, if he gave only general information, all the details would be found out in his letters. Start fixing the bug, only after the client confirms the need for changes.
Software quality assurance companies help to detect bugs during the SDLC, they monitor the development process to ascertain that the quality standards are being met. Without controlling each stage it would be difficult to ensure successful release of your project.
If you were able to reproduce the bug but agreed on the need for changes, then estimate the time required for repair (check this time with the programmers) and testing. Inform the client about the commencement of work and the timing of its completion.
Check that you have been aware of all the preconditions and are able to reproduce the bug in your test environment. Check if there are any unnecessary steps to playback, and also whether all the cases in which a bug is played back are found.
Check that the bug is not reproduced after it is fixed and inform the client about the completion of the work.
Support is help provided to users (in order to solve their problems). Most problems arise after the new code is uploaded to the product site. Work on bugs that users reported, is carried out according to the same rules as those applying to client ones. The only difference is that it is very difficult to reproduce them and it is even more difficult to understand what exactly leads to an error. It happens that a whole day is not enough to figure out what is wrong.