[GadgetKen]

Sorry to hear the local sim didn't work out. Haven't visited Chile, but a couple of thoughts:

Could you maybe buy a prepaid international calling card that has a local Chilean access number? Assuming Movistar doesn't block the number, you could place international calls using 2 stage dialing. Not as convenient as direct-dial but it's a work-around. Maybe you could store the calling card and pin number in a speed dial location on your phone.

You might also be able to use a call-back service to accomplish the same thing if it has a Chilean local number.

There are some international sims that claim Chile coverage including Travelsim with an Estonia number(also rebranded as Telestial Explorer), or Geodesa or one of the other Isle of Man cards. If you need a spare card to your United Mobile card it might be worth a try. Telestial does sell some international cards (I also found a discount offer on their United Mobile refill page for buying 2 of these because they no longer sell United Mobile/Riiing sim cards; I might take them up on this).