Best answer by mattj3135
Sorry to hear this
As long as you're still in your 14 day cool off period, message the Boost Care team for them to cancel your switch.
You can do this by, either, reaching out to their Facebook page or Twitter page. or by popping them a call on 0330 1027517, between 8am - 8pm, Monday to Friday or between 9am - 1pm on Saturdays.
Updated 27/02/2020 - Added quick links to Boost Facebook and Twitter pages.