Which service center? I think you can do the follow:

1. As to the membership, you may write to the presidents of the society to explain the nature of the societies, and the criteria for membership.
2. If you reviewed for a journal, you may ask one of the editors to provide a letter stating you contribution as a reviewer to journal, and you expertise to the field.
3. you can provide a list of citations from google scholar to show that most of the citations were not self ciatation.
4.do the rest accordingly

good luck!