Caller Reject is a chargeable feature which lets you block nuisance or unwanted calls by stopping them getting through to your business landline. You can block up to 10 numbers. Some calls from international destinations can’t be barred as the number isn’t always presented.
Some callers have an 0800 number which is displayed rather than their network number. If you choose to reject and block one of these numbers, the network (underlying) number will be blocked but not the 0800 one.