dd's and standing orders can be set up for the 28th 29th 30th & 31st so this is not entirely correct. if that month doesn't contain any of these dates it is debited on the previous day. the bank uses a payment diary code called ldm (last day of month) for most end of month payments, so the payment will be taken on the last day of that month whatever the date. as for the mobile phone company, yes they can take out the direct debit when they want. however their computer will do a tape run to collect all payments on a certain date every month. this collects all bills at once. that is why they will not do this on a date which suits you. it would be causing them more work. hope this helps