"The network is full, try later" with leak

Hi, since I update the os like 3 months ago from several leaks, 10.1.16xx/17xx/20xx, I'm on 10.1.0.4543 and every time I make a call to gf, same carrier, iPhone user, I get an annoying sound and a message that says the network is full or busy, try again later. After a few try, I get to make the call. It seems only happen with my gf. I know the carrier network isn't full or something like that because I try to call another phone and it is possible. When she tries, never ring on her iPhone, like no noise, and end it.

What could it be?
I'm on Claro Per, stl001, 10.1.0.4543, and of course the message in Spanish is like this
"Lo sentimos la Red esta ocupada, intntelo nuevamente"

Some Spanish speaker could traduce better than me? I'm missing something on settings, because two months ago I didn't have any gf, but now it's annoying. Lol

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