Do you have the phone itself or the SIM set as the storage location for contacts? Entries on the SIM can only contain one line (ie a name and a number), but the on-device option sometimes has more flexibility. It's not clear from the manual whether this is the case, but it does seem to refer to two possible locations.
The downside of using the device when it's a simple one that doesn't sync with an online account can be when it comes to transferring to a different one. Contacts on the SIM will simply move over with it, as long as the new device accepts the same size, of course. The Vodafone instore Red Box service may be able to help in both those cases, though.
