Set up Phone System in your organization

 https://learn.microsoft.com/en-us/microsoftteams/setting-up-your-phone-system

• Step 1: Buy and assign a Phone System license
• Step 2: Choose a PSTN connectivity option
• Step 3: Get phone numbers for your users
• Step 4: Get phone numbers for services
• Step 5: If you want to set up a call queue
• Step 6: If you want to set up an auto attendant
• Step 7: Set up communication credits for toll-free numbers