How do I know if a smartphone is locked to a network or unlocked ?

Im going to be getting a phone from a friend this week but he does not know if it is locked to EE.
I want to use O2 for a special offer that ends on 13th June so I have 3 questions:

1. How can I check to see if his phone is locked to EE ?
2. If I insert my SIM from my existing phone, will that allow me to check if its unlocked ?
3. Will it wreck my SIM data by inserting it into another phone ?
4. If his phone IS locked and he has now got a new contract with a different phone with EE, can it be unlocked by his requesting an unlock from EE for free even though it is no longer his current phone ?
Thanks
 
Solution
A locked phone may either
1/ Not work with the new network

or

2/ Not recognise the SIM card.

It WONT cause any damage to either SIM or phone to try it.

Chances are, if he bought it with a timed contract, it will be locked; if the contract is up, he can ask them to unlock it and they should do so; however if the contract isnt up, they wont; as he still hasnt finished paying for the phone.

CaptainCretin

Respectable
Jul 18, 2016
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A locked phone may either
1/ Not work with the new network

or

2/ Not recognise the SIM card.

It WONT cause any damage to either SIM or phone to try it.

Chances are, if he bought it with a timed contract, it will be locked; if the contract is up, he can ask them to unlock it and they should do so; however if the contract isnt up, they wont; as he still hasnt finished paying for the phone.
 
Solution

Math Geek

Titan
Ambassador
right if it was bought through a specific company, then it is almost 100% guaranteed to be locked to that network. sadly even if he bought the phone outright it is likely still locked. only way to get it unlocked is to ask the company he got it from to unlock it for a new network.

they may or may not do it depending on factors like cretin listed above. though O2 may have some luck getting it unlocked through their own channels but may not be able to either.