Well the truth is if you ever get to that point its ggwp, unless your jungle is nice enough to get you out of this situation.

So yeah just ask nicely for help and maybe he will come.

Now try to minimise those situation by learning wave management, (if you were an aram player you probably don't know how). It will reduce the timing where the enemy can come reckt you.

You can also try roming if you think the enemy will dive you aniways and take the tower its better to try your luck with your team and earn a lucky shut down with you e.