Mayor Adrian Fenty is going to make an official announcement next week that the Mayor’s Citywide Call Center, currently 727-1000, will change its number to 311. Yesterday on the MPD-maintained email listserves, a police spokesperson posted messages indicating there had been a change in policy in when and under what circumstances residents should call 311 versus 911. Penn Quarter Living pointed out the message on the 1st District listserv, and we found a similar one…