Locked iPhones won't work with local SIM cards abroad, potentially leading to massive roaming fees.
Fortunately, checking your iPhone's carrier by serial number is a relatively straightforward process. Here are the steps: iphone carrier check by serial number
The short answer is While the serial number can provide useful clues, it is not the definitive tool many assume it to be. For a truly reliable carrier check, other identifiers—specifically the IMEI (International Mobile Equipment Identity) or the MEID —are far more effective. Locked iPhones won't work with local SIM cards
Free serial number checkers are often scams. They may show you a "clean" carrier status to make you buy, but they are pulling from old caches. For accurate results, you generally have to pay a few dollars. For accurate results, you generally have to pay
– Apple itself will not directly tell you the carrier lock status for privacy reasons, but they can confirm if a device is “activation locked” or has a valid purchase date.