Comment by chokma

It's also a good idea to cancel services via mail and to demand a written response confirming the cancellation. Otherwise, Vodafone (from your example) may conveniently forget the exact date of your cancellation... and good luck proving you cancelled an account on time if the confirmation SMS is now stored on a no longer valid SIM card, you cannot prove anything.

Yeah, Vodafone ... still sending invoices which deny I cancelled my contract half a year ago.

edit:grammar