Can I cancel sky mobile...

[P4nda]

... mid contract because they are blocking impotant OTPs, specifically from NS&I? Hence I can't log into my account. 

[Gordanx_x]

You can definitely cancel your sky mobile contract although there would be an early termination fee if you're in a contract but you could still have a word with their cancellation department and explain the problem to them they may be able to figure something out.