Purchase IMEI unlock codes for the HTC Explorer to allow it to be used on all networks.
A network lock, otherwise known as a SIM lock, is a control placed on the phone by the original network that sold it. They are able to do this because with the lock, they can then sell the phone for cheaper, offering the customer a better upfront deal. This lock does however stay with the phone permanently unless it is removed with an unlock code or software. Doing this is completely legal and won't impact your warranty in any way.
In the emails that we send out for HTC orders, we only need to send 1 unlock code. This code is the one that is unique for the IMEI that your supplied and will work on nearly all networks. This is an extremely simple process and one that HTC have deliberately worked on. We also provide the instructions to enter the code for each HTC mobile phone, so you'll know exactly what to do.