In short the customer service telephone number for Vodafone is 0333 304 0194. This telephone number can be used to manage your account and for billing enquiries, including to set up a direct debit payment. When you call vodafone you will need to provide security details such as your 4 digit pin code, your account number and the first line of your address.
Calls to this number can be a bit frustrating as you will first be met by an automated line. Bear with it and they will send you through to a human being with whom you can actually get your account sorted.