Should we call on Jesus or Jehovah to be saved?
The question assumes that God the Father and God the Son have different desires for our salvation. Yet Jesus stated, "I do not pray for these alone, but also for those who will believe in Me through their word; that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me" (John 17:20-21). Being one, there is no difference in purpose between the Son and the Father. Earlier Jesus also stated, "I do not seek My own will but the will of the Father who sent Me" (John 5:30).
To call upon someone is to appeal to their authority or to claim a right that someone had authorized. For example, Paul called upon the name of Caesar when it seemed he would not get local justice (Acts 25:11-12). It was Caesar who authorized the right to appeal a judge's decision, so Paul called upon Caesar's law for protection.
Sin has interfered with our relationship with God. "And there is no one who calls on Your name, who stirs himself up to take hold of You; for You have hidden Your face from us, and have consumed us because of our iniquities" (Isaiah 64:7). Yet God has offered to save those who will call upon His name -- that is, to appeal to His authority. "I will bring the one-third through the fire, will refine them as silver is refined, And test them as gold is tested. They will call on My name, and I will answer them. I will say, 'This is My people'; and each one will say, 'The LORD is my God.' " (Zechariah 13:9). This Peter quotes in Acts 2:21, "And it shall come to pass that whoever calls on the name of the LORD shall be saved."
Since God gave Jesus all authority ("You have given Him authority over all flesh, that He should give eternal life to as many as You have given Him" - John 17:2 see also Matthew 28:18), Peter boldly states this about Jesus: "Nor is there salvation in any other, for there is no other name under heaven given among men by which we must be saved" (Acts 4:12).
Of course, to appeal to a higher authority assumes you understand your rights and believe that God has the power to lift you up. "For there is no distinction between Jew and Greek, for the same Lord over all is rich to all who call upon Him. For "whoever calls on the name of the LORD shall be saved." How then shall they call on Him in whom they have not believed? And how shall they believe in Him of whom they have not heard? And how shall they hear without a preacher?" (Romans 10:12-14). Interestingly, baptism is an act that is described as "calling on the Lord." "And now why are you waiting? Arise and be baptized, and wash away your sins, calling on the name of the Lord" (Acts 22:16). It is not an act that earns salvation, but it is an appeal to the authority of God. "Corresponding to that, baptism now saves you--not the removal of dirt from the flesh, but an appeal to God for a good conscience--through the resurrection of Jesus Christ, who is at the right hand of God, having gone into heaven, after angels and authorities and powers had been subjected to Him" (I Peter 3:21-22).
See "All in a Name" for more details.