There is no textual basis for believing verse 13 and verse 16 represent two different speakers. We know there was an angel, a messenger sent to John to carry these words, but John is careful to distinguish the messenger from the message. But if you want agency, here’s a great example of it, because the text makes clear the agent is empowered to speak on behalf of one principal, Jesus, and when he does so, he speaks in the first person, as he does when claiming to be Alpha and Omega. Jesus is God.
Rev 22:12 “And, behold, I come quickly; and my reward is with me, to give every man according as his work shall be. [13] I am Alpha and Omega, the beginning and the end, the first and the last. [14] Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city. [15] For without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie. [16] I Jesus have sent mine angel to testify unto you these things in the churches. I am the root and the offspring of David, and the bright and morning star.”
Peace,
SR
Rev. 1:6 and 8 shows that the Alpha and Omega is not Jesus the Son but Jehovah the Father.
And when the speaker changes in verse 16 the speaker is identified as “I, Jesus” and a not just continuation of the previous speaker.
The Alpha/Omega is identified as God, the Father, his father, whom Jesus called “my God”.