How to contact my SIM provider?

Call or visit your carrier.

Who is my carrier:

Go to -> Settings -> Mobile network -> scroll to Network selection you can see who your carrier is.

See this Apple article: How to unlock your iPhone for use with a different carrier

How to unlock your iPhone for use with a different carrier - Apple Support

• Apple can't unlock your iPhone for use with a different carrier. Only your carrier can unlock your iPhone.

You need to contact your Carrier.

Or do you need the PUK code?, See this Apple article: Use a SIM PIN for your iPhone or iPad

Use a SIM PIN for your iPhone or iPad - Apple Support

You’ll have to call your carrier’s customer-support number from another phone.

Or contact them online (as you’re obviously capable of doing).

Do you have a SIM card?

How do you know the SIM card is locked?

If there is no SIM card in the phone, look for / visit a carrier, take a subscription, postpaid or prepaid card.

Check whether the SIM card is suitable for your iPhone.

Hopefully you have an carrier unlocked iPhone.

See -> If you can't activate your iPhone or iPad (Wi-Fi + Cellular)

If you can't activate your iPhone or iPad (Wi-Fi + Cellular) - Apple Support

• If you still can't activate your iPhone or iPad, contact Apple Support.

Call or visit your carrier.

If you don't have a phone you can use, borrow one from someone close to you.

Check out their website online.

Google is your friend. You can obviously access the Internet. Look them up.

Who is my carrier:

Go to -> Settings -> Mobile network -> scroll to Network selection you can see who your carrier is.