REQUEST TO HAVE MY PHONE SIM CARD LOCKED

I got a second hand iphone model A1524 , IMEI: 355384071620214 from a friend who has been using it in Manchester UK.

when i tried to put in my Uganda Airtel line for use, it could not allow. a message "the sim card you currently have installed in this iphone is from a network provider that is not supported under the activation policy currently assigned by the activation service." How can i be helped so i make use of my phone.

Thanks for the kind assistance given.