Cannot add second SIM to same account

Hi there.

Sorry to hear your having issues adding another SIM.

If not done so already, please raise a chat with our Customer Support Team, they can look into this further for you, they are online 7 days a week between 8am-8pm and can be contacted directly here https://smarty.co.uk/contact
Remember to ask to 'talk to a PERSON', rather than the bot.
Have a great day! -Adrian.