How can I allow my colleague (same org.) to open a call/meeting I created...?

Hi,

In case you are scheduling the meeting from the Outlook you have an option of Meeting Option. In the Meeting Option look for the option Who can Start the meeting and select the option as People within my organization.

Post the meeting invite is send the settings can be modified as well as before sending the meeting invite we can also share configure the same.

With Regards,
Satish U

Hi BAlDana If it's a regular Teams meeting, anyone who is invited can start the meeting.  What type of issues are you having?

Microsoft Teams- Can anyone "start" a meeting? - Microsoft Community