> You actually have to keep their account active and make it work somehow. If you can't...
If you don't, not if can't. If you can demonstrate a reason that that piece of information is absolutely necessary for your service then you can deny service if the person doesn't want to provide the data. Otherwise you could submit a complaint about any delivery service for refusing delivery if you refuse to give them your address.
If you don't provide a reason why that data is necessary and still require the person to give it to you, then yes, you're in for some pain.
If you don't, not if can't. If you can demonstrate a reason that that piece of information is absolutely necessary for your service then you can deny service if the person doesn't want to provide the data. Otherwise you could submit a complaint about any delivery service for refusing delivery if you refuse to give them your address.
If you don't provide a reason why that data is necessary and still require the person to give it to you, then yes, you're in for some pain.