You don't need to sign in to get in touch on chat. It would be best to contact chat on a laptop or desktop, on your sign in page there should be a blue box in the bottom righthand corner of the page, click on that, the chat box will pop up and ask you to sign in but if you can't don't just click continue. Ask for or type live agent or you will be conversing with a robot.
You can also get a hold of customer service by Facebook messenger or Twitter, both icons are in the bottom righthand corner of this page. I prefer FB messenger myself.
They will likely need to reset or re-provision you SIM.
