IEEE rejects my paper saying that it is plagiarised
To answer your question, yes you can and should write back to the editor and request that they provide the information related to this accusation of plagiarism. Such accusations are quite serious and they should not make them without being willing to provide support for their claims. It would be entirely unreasonable for them to refuse to produce evidence. 

In the event that they will not detail why they are making claims of plagiarism, and you are absolutely sure you have not inadvertently plagiarised,  I would suggest you bring the matter to whatever office or work group in your University deals with aspects of academic integrity. They may be able to put more pressure on the journal to produce evidence.