This is quick and dirty, some or all of this info might be wrong. I just stumbled upon this while testing something else and SCRLog was running and told me what happened. Reset and Tirean want this figured out. Feedback, please.

Katie can block your calls. The entire time the GFMEET thread makes it possible for you to get her as GF, calls are blocked. Katie is not always there so the blocking probably does not always happen. It probably depends on weekday / time of day. There are two rectangles the game checks. If you are in the inner one, calls get blocked until you are not in the outer one anymore. (original map: http://www.ehgames.com/gta/map.html?4ps7lx8rube)

It's probably better to hold and cancel calls or to use Vigilante to set the call timer to 0. I mean: start Vigilante, cancel it 15s before you need the call. Start holding a call, cancel the call 15s before you need it. It should be 15s (not 16.5s) in both cases.

The call holding thing can also be used to avoid the call before Riot. Your phone rings immediately after Cut Throat Business. Hold that call and cancel it while getting out of your car at the mansion. No call comes in for the next 15s which quite likely is enough.

correct

Thanks. :D

you're welcome,anything else you need my expertize on? Kappa all jokes aside, i was 99% sure the area you were in was preventing the call from coming in, just needed confirmation like this