If you bought your cell phone from a mobile operator, it will most likely be blocked or "simlocked". That is, it will not accept any other SIM card than that of the operator from whom you bought your mobile.
To be able to use your mobile phone with a SIM card from another operator, it will have to be unlocked or "unlocked" because when you try to use another SIM card, you will most likely receive the following message " PIN code for unblocking the SIM network ".
If you bought your mobile phone for more than 3 months, the unlocking is free. Under 3 months, the unlocking will be billed to you 76 euros on the next bill from your operator.
To unlock your mobile phone, you will need the IMEI code of the mobile phone (IMEI = "International Mobile Equipment Identity", it's a unique number that identifies your mobile phone).
To display it, just dial * # 06 # on your mobile phone.
( star -> pound -> 06 -> pound then press the Call key on your telephone).
This IMEI code is usually also written on the bottom of your laptop battery. Once the IMEI code is in your possession, you can contact your operator's telephone customer service or choose the online unlocking request:
Call 634 from your mobile
Call 1023 from your mobile
Call 3970 from your mobile
Unlocking or "unlocking" your mobile phone can take between 2 hours and 5 days depending on your operator.
If you are a customer of a virtual operator (MVNO) who uses the network of one of the 3 aforementioned operators (such as NRJ Mobile , Universal Mobile , Virgin Mobile , etc.), you will have to go to your online customer area to find the link that will allow you to unblock your mobile or call the customer service of your operator directly.
Choose the unlocking solution from your operator's online customer area, it is generally faster.