already had a warning for all members on the website
Listing your name on the deafVP directory provides information allowing anyone with a videophone to call you. Use discretion when answering calls from people you do not know. If you do not recognize the name of the caller, you can select the "Reject call" option on the caller ID notification of the incoming calls. If you have problems with "prank" calls, you might consider removing your listing, on the deafVP directory.
So if you do not recognize then reject and delete. *shrug* (but look below)
by the way, they do not need to be signed in to send you this.. they just click a button to request your number and there's a textbox which they fill in those text you saw.
BUT: if it is a scammer, then don't do anything... just delete it. why? they filled in those boxes with email addresses which is useless because when you reject, they don't get anything back from you. If it is real and not a scammer then the accept link does work.