Nokia 5310 makes a sound similar to a dial up modem when I call a specific person

Hey,

I recently bought a blue Nokia 5310. I bought it for the sole purpose of having a matching pair with my girlfriend who already has a red Nokia 5310. Now, whenever I try to call her, the phone makes a sound similar to dial up modem connecting to the internet. After a few seconds of this horrible sound (Reminds me of the days when we all ran on dial-up and I got booted every few minutes...terrible times), the line gets dropped. I can never successfully connect to my girlfriend. I can send text messages to her just fine. I can call everyone else just fine. Any other phone can contact her cell phone just fine. Does anyone know a solution to this? I would try to return it to the store but I live in a country where the main spoken language is NOT English. The girlfriend is currently on vacation and I cannot ask her to translate for me.

Thanks,
Max

Edit: Forgot to mention that I can call her on any of my other phones using the same SIM card.

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› See More: Nokia 5310 makes a sound similar to a dial up modem when I call a specific person

Sure you're not calling a fax machine or an actual modem? Either that or the switch that is routing your call is bad and you getting connecting to one of the two.