Could you have a friend or someone in your office take care of utility service cancelation on your behalf when you leave Japan?

For some things yes, but many companies are very strict about personal identification these days, especially NTT and Sky Perfect TV.  If the vendor has an English customer service number, I suggest that the call be made in person.

Bank accounts and mobile phones need to be cancelled in person by visiting the store or branch office. Especially for mobile phones, you need to be careful to let them know in whose name the contract is as it needs to be the contract holder reporting the cancellation.  The phone will be disconnected immediately so this should be done shortly before your departure.

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