That doesn't sound right, @DianaHa_2549027 - have you checked if your old service provider's SIM card is still working or not?
In any event, your switch might've suffered a split-port, whereby not all the network services are being routed correctly to your SMARTY SIM card.
I'd recommend contacting the SMARTY customer service team about this issue asap, @DianaHa_2549027.
Contact SMARTY online at https://smarty.co.uk/contact, then scroll down to "start a conversation". The advisers work until 8pm everyday.
