How to upgrade to a paid account on heroku?

Question

Heroku

The option to deploy the bot on Heroku (in a regular free account) is only suitable for testing. After ~25 days, the bot falls asleep and stops responding. Moreover, adding a new application to the account also does not give anything new - the bot does not work.
How can I switch to a paid account so that the bot works without such a narrow limit? Tried to search, but for some reason there are no such oriented articles.