@Tharshin , have you reported your device as lost or stolen? This you need to do and then EE will send you a replacements SIM card and blacklist your device, this is the only way to do it. See my signature for contacting customer service.
To contact EE customer service dial 150 from your mobile phone or ring customer service for free using web based app or another phone: +44 800 079 8586 or +44 800 956 6000.
