Unlocking a phone

[robbocop33]

Trying to help out a friend who lost her phone,and for whatever reason her insurance didn't pay up.I said i had an htc 10 lying around for ages in the house.I tried to unlock it before i give her it but when going through the unlocking question on sites i honestly can't remember who the service provider was for this phone(4 years or so ago)
Is it vital they have the correct old service provider name?i have the imei for the phone.
What's the easiest way to get this unlocked?Thanks.

[mmm-five]

Do you not have any email bills or comms from the service provider back from 4 years back?

[Saleen836]

If the old phone was on contract check on your credit score website as this should tell you who the contract was with

[x5tuu]

Lots of older android phones had a network splash screen when turning them on/off - does this one not? Could be an easy way to tell?!

[gus607]

My son once gave me his old company phone. Tried everywhere for quotes to get it unlocked & in the end just stuck a THREE sim card in & it worked a treat. Wasn't locked to any network at all !

[robbocop33]

Just found out it was on Virgin contract,read that they don't lock their phones on a contract?
I temporarily put the sim of my new phone in it and the phone wanted me to transfer everything off this sim!So that must be promising?