Simple ways to view your call history

On an iPhone, launch the Phone application → Recent events. For details, tap on an item: number, time, or length.
On Android, launch the default Phone / Dialer app and select the Recents or Call History. Tap on an item to learn more about it. The UI is different from company to company, but the underlying idea is the same.
If the log was removed, legal recovery options

Restore from backup
iPhone: You could try restoring an iCloud or iTunes backup, which was created at the time the calls were made.
Android: Some backups and some devices include call history (Google Drive or OEM backups); a device restore might just bring your calls back.
Official carrier records: Mobile carriers store Call Detail Records (CDRs). Request that your carrier provide you with your own CDRs. You may be required to show identification and/or submit a request in writing. The length of time that carriers store information varies depending on the country and carrier. In general, a court order or consent is required to obtain another person’s CDRs.