Cell phones are for emergency access (the site is down, etc) and only given in specific situations for specific rates. That does not sound like the case here. The client was given a phone number that would go to his cell at specific times which was more than sufficient.
Having regular phone contact is perfectly fine and can be scheduled for regular meetings. Weekly status meetings on ongoing work. Pre and post-launch meetings for specific milestones. Things like that. A client that wants license to call your cell whenever they think of a random bit of information instead of sending it in an email or saving it for a scheduled phone meeting (or scheduling one specifically for it) is not a client you want to have. They clearly don't value your time or the fact that you have other clients and responsibilities.