It is evident from vs 9 that in context we are talking about Jesus.
“For if you confess with your mouth that Jesus is Lord and believe in your heart God raised him from the dead, you will be saved”
Verse 14 says “how will they call on him if they have not put faith in him”
lets think about this. Who is speaking? (Paul) and who is he talking about? Who is the “they”? (The Jews). Obviously the Jews knew the Lord was Jehovah. The one they needed to call on was Christ. The one they needed to believe in was Jesus.