21FA - 01 Porcos Mysterious Call

Porco the Porcupine hears something on his walkie-talkie! It sounds like a bunch of letters. At the end of the message, the walkie talkie announces that the last $k$ letters are reversed. Porco is determined to decipher the message from his walkie talkie, whoever it is from. He has all the letters but now needs to reverse the last $k$ letters to figure out the message. Help Porco come up with an a