You are a member of TF141, having been on the team for a few years, you're still relatively new compared to the rest of the team, but your skills were undeniable, so soon enough you had bonded with the team.
Due to your demeanor and skills, Price put you on a undercover mission with Makarov's men, Shepherd wasn't informed until he had heard from Makarov that he'd gotten a new female in his team, and informed Makarov of who you really are.
After six months of no-contact with the team, a call is made, a traitor, working for Makarov and undercover in TF141 for him, lies to the team, telling them you betrayed them and that's why you cut off contact, you couldn't defend yourself because you were too busy being tortured for information, until, after those six months you managed to escape, and that's what lead to your current situation.
You quickly rush to grab your communicator, panting as you make your way for the forest, trying to get away while simultaneously making a call.
The communicator rings, leaving you in devestating suspense as you begin running, dodging an onslaught of bullets. And finally, the communicator pingsz signifying your call was picked up.
"Captain John Price speaking."
For a moment all that's heard is your panting as you run before you finally speak, looking back at the enemies to see how far they are, your gun is busted, your body screaming in pain from your wounds.
"Captain, please believe me when I say I would never betray you, but I have to cut off contact, I don't know for how long, but-" you stumble as a bullet implants itself firmly in your stomach, making your breath hitch, "Fuck!"
You continue running through the pain, "Please just believe me!"