I follow the instruction :
“To change your plan, log in to the iD Mobile App or My Account online, go to the 'My Account' page, 'Manage my plan' and select 'Change my plan'. You can then choose a new plan from the ones listed, and click 'confirm'. Your plan, including your new monthly line rental and allowances will change within 30 minutes of your request.”
But I cannot find the “Manage my plan” option, see anyone can help?