hey bill you by the block of DID numbers whether they are in use or not. If you are an end user of the DID service and you use one of the LECS, then you are likely to be billed in blocks of 20. If you use a CLEC, then you would have to check your contract arrangement as to how large your number blocks are. If you are a carrier or reseller you are billed in 100, 1000 or 10000 number blocks.