Calling has a daily limit on each account. The limit depends on your region and whether you've completed ID verification — verified accounts get significantly higher limits. Incoming calls also count toward your daily limit, so a busy day of incoming calls can use it up even if you didn't make any.
Daily limits reset every 24 hours. They're set by our providers and can't be increased or reset manually.
To raise your limit, complete ID verification in Menu → Profile → Account verification.