To find out whose number is calling you for free, you can use several online reverse phone lookup tools that identify the caller by entering the phone number:

• Truecaller offers a free reverse phone lookup tool where you enter the number and get caller details within seconds

• IPQualityScore (IPQS) provides a free phone number lookup service showing carrier, line type, location, and sometimes owner details

• NumLookup allows completely free reverse phone lookup for US numbers without registration, providing the owner's full name and other info

• Whitepages offers free reverse phone lookup for landlines and business numbers, showing name, address, carrier, and spam reports; cell phone details may require a fee

• Sync.ME app identifies unknown callers and blocks spam calls, showing caller ID even if the number is not in your contacts

Other methods include searching the number on social media platforms or apps like Facebook, Snapchat, or cash apps to see if the number is linked to a profile

. In summary, you can use free online services like Truecaller, NumLookup, IPQS, or Whitepages to identify who is calling you by entering the phone number. For more detailed info such as addresses, some services may charge a fee