Cancelled monthly contract sim the day it arrived but still charged

[obvious]

I cancelled a monthly contract sim on the day it arrived. I purchased online through the o2 website. I haven’t opened it or used it but a month later the direct debit of just over £30 was taken out though the monthly contract was £21.

I cancelled under the “change your mind” cooling off period on day one and there was zero usage since then.

Should I have incurred any charges under the change-your-mind provisions under the circumstances?

 Thanks

[MI5 · Accepted solution]

@obvious 

No, there should be no charges at all.

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