Unlock sim card error from Iphone 7

if its over two 1/2 year old its free to unlock from any carrier just ring the provider and ask for unlock code i do this all the time i have never had a new phone.

Try a sim card from a carrier that is not for the phone. If your carrier is boost mobile then use a Verizon or sprint sim card, even a new sim card will not work if it is the carrier locked to the phone. It must be a non carrier sim card.

With a geevy SIM card

1. Unlike Sprint, the SIM slot on Verizon iPhones comes unlocked. Caveats: While you can use SIM-equipped Verizon phones on AT&T, T-Mobile and other GSM carriers, unless the device has roaming GSM radios it won't be able to make phone calls or send texts in the United States.Jul 28, 2014

   Now that it's legal, here's how to unlock your phone on all ...

   https://gigaom.com/2014/07/28/unlock-phone-att-verizon-tmobile-sprint/
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How to unlock your Sprint phone or tablet - WhistleOut

www.whistleout.com/CellPhones/.../how-to-unlock-your-sprint-phone-or...
Mar 12, 2015 - Home>Cell Phones>Cell Phone Guides>How to unlock your Sprint

The iPhone 4 cannot be unlocked from Verizon due to not having a sim slot

I’m happy to help further over the phone at https://www.6ya.com/expert/susan_42b401e0b1603d8a

Depending upon whether your phone has been locked or if it's unlocked you can switch SIM cards around with no problem.

A phone being locked is when the service provider has blocked the phone from being used by any other service provider's SIM cards. Usually you will be asked for a PIN in order to allow the new SIM to be used. If you do have a locked phone then you can do a search online for unlocking your phone. The link below is for use in the UK, so you will have to go to google.com and use the search string "unlock..."
I believe that Verizon and Sprint phones are ussualy locked down, i would check the status of your SIM card, you should be able to use your hardware however you need the service and in this case a verizon SIM card.
a possible solution would be to buy a cheap verizon pay-as-you-go phone and remove the SIM card and put in your phone, you may have to unlock your phone to accept it.

Good Luck!

this is what you do

1. get a unlock card Click Here
2. get a Verizon Sim card click here
3. Switch off 3G network: Setting---General---Network---Enable 3G---Off
4. Turn off the iPhone 3G, take out the SIM tray, place the Unlock Card and the SIM card on the SIM tray, put back the SIM tray into the iPhone
5. Turn on the iPhone
   There is NO NEED TO CUT YOUR SIM!
6. Just Plug & Play!

yes unlocking is always possible visit ur local mobile mechanic

If he used it for the same carrier you are on (ie: sprint, AT&T, verizon, etc..) then it may just be a different format SIM card. Over my past 3 phones, I have had to change sim cards twice. Good thing is, usually the carrier doesn't charge for this. For example, if I took the sim out of my current LG g6, and tried to put it in my old galaxy note 3, it wouldn't work, I would have to get one of the older style SIM cards.
On the other hand, sometimes you won't be able to take a phone from one carrier to another, even if it is unlocked. It all depends on the cellular technology that the phone supports.
Hope this helps.

this is what you do

1. get a unlock card Click Here
2. get a Verizon Sim card click here
3. Switch off 3G network: Setting---General---Network---Enable 3G---Off
4. Turn off the iPhone 3G, take out the SIM tray, place the Unlock Card and the SIM card on the SIM tray, put back the SIM tray into the iPhone
5. Turn on the iPhone
   There is NO NEED TO CUT YOUR SIM!
   
   
6. Just Plug & Play!