Change number while in the middle of the contract due to stalking/harassment

[HellOnEarth]

An ex boyfriend who lives in the US got hold of my number and has been harassing and stalking me ever since.
I can block the US number he uses but he can just get a new one and the harassment starts all over again.
Is it possible to bar all incoming international calls and texts and WhatsApp messages from within the O2 account or can I then change my number while my contract is still running? I could pay off the device and switch the number but at the moment I don't have the money to pay it off and that takes a few days anyway. I need this done asap as this is stressing me out considerably. Thanks.

[Bambino · Accepted solution]

@HellOnEarth O2 will allow you one free number change. You need to speak to customer service to get this done. All available numbers are in the link below. Try 0800 587 4005 first.

Guide: Coronavirus Community Help and Support 

[Cleoriff]

A community guide here (I'd forgotten we had!)

Guide: How to change your mobile number 

[HellOnEarth]

Thanks for the replies!