Gearing down while cycling up a hill will make your journey so much easier.
And therefore you don’t have to stand up and strain yourself while doing so. And if your phone should ring while cycling up said hill, find a safe place to pull into and then answer.
Not try to dig it out off your pocket, while standing up on your bike while riding up a hill.
Because there is a good chance that you will drop the phone, ride over it and nearly come off the bike when you clip the kerb, which you duly did today.