Most people who own an HGVC-developed resort and an HGVC-affiliate resort have only one account number. It is important when purchasing an additional week to make sure that the names of the owners are exactly the same as used in connection with the first week. For example, if you and your spouse own the first week jointly, you should own the second week jointly, too. Otherwise, Hilton might set up the second week using a new account number, which would probably require you to pay for a new account to be set up.
Our weeks are all in the same names and we have only one HGVC account. We don't have to make any reservations by phone. The affiliates we own are fixed weeks, so if we want HGVC points rather than to use the fixed week, we do have to call HGVC and ask them to cancel the fixed week reservation. When the club cancels the week, it adds the proper number of points to our account balance (if the week is a platinum 2-bedroom week, it adds 7,000 points; if it is a gold 2-bedroom week, the club adds 5,000 points, etc.). Once the fixed week is canceled, "points are points," all of them are treated the same, and all are available for phone reservations or computer reservations, whichever you prefer.