usually, reviewers are chosen carefully but of course can't be perfect.
If you know the reviewer, starting a dialogue usually is the fastest way to set things straight.
If you don't know the person and have no means of contacting him/her, try contacting the organization that established the reviewer and state your concerns.
If you have valid proof the reviewer is wrong, try asking for a second opinion from a different person but be prepared to get the same result.
If you do and a second reviewer has the same concerns, maybe you think about the paper again.
If the second reviewer has an opposite result than the first one, only one of them can be true.
Organizations usually would appreciate any feedback on reviewers to improve the review process. In case you reviewer turns out not be the expert to ask, most likely the organization will not give a paper from this topic to him/her again.