You may communicate with your matches through both sites.
Both testing companies provide lists of your DNA relatives (called matches), unless you opt out of DNA matching, as well as robust tools for exploring your matches. Both report how much DNA you share with each match; the length of your longest segment of shared DNA (which has implications for how distantly you may be related); match-labeling tools; and tables showing possible genetic relationships for each match. You may communicate with your matches through both sites.