Instead of asking this question you could quickly make a search on google and find out if Telegram actually existed back then because it was initially released in 2013,a long time after bitcoin was launched. I wasn't very active online back in 2009 and I don't know what apps they used back them for communicating in groups but I guess there was something similar to telegram.
There were too many messaging apps back then . few to name are ym , ebuddy , skype , nimbuzz , irc , etc....
I believe that satoshi n. Did also use one of the apps that i listed above because those apps are too useful for comunicating . he might have a team and they are working together for the creation of bitcoin .