Medusa sos call

Hey, I got a sos call from Medusa but at the time I had a fairly substantial amount of money I hadn't banked, and 5-0 take all unbanked surplus cash off of you if busted, so I couldn't risk it! I decided to bank the money at the save house, then I immediately went back to free roam but Medusa didn't call again and now her garage is £35k to unlock. I can buy it but I want to do the SOS mission instead. Any ideas on how I could get the game to prompt me with the SOS mission again please? 

Thanks.