How do I know my iPhone carrier?

• Do you pay the bill?
• Do you see it listed at Settings > Cellular?
• Do you have a physical SIM card that may have it stamped on there.
• Did you purchase a device that is SIM locked?

Do Settings > Cellular. What does your phone show where "CC"appears in this image:

Who do you pay for the cell service?

They are the ones you pay for cellular phone service. Surely you know who you are paying every month.

If you're trying to say you purchased a carrier locked phone from someone an you don't know what carrier it's locked to, ask whoever you got it from.

Seriously ??? 🙄

Don't know who my phone carrier is

Really? You pay your carrier each month for cellular service.

Are there some things that you are not telling us? Did you buy a phone that is carrier locked?