It is true that to "call on the name of [XXX]" in the OT Hebrew idiom is to:
- recognize that entity as a god
- seek help from that entity, eg for salvation
- effectively to pray to the entity as a god.
This occurs numerous times in the OT such as Joel 2:32, 1 Kings 18:24 (&25 for Baal), 2 Kings 5:11, Gen 4:26, 12:8, 13:4, 21:33, 26:25, Ps 116:4, 13, 13, 17, Zeph 3:9, etc.
In the case of the Israelites, they were instructed to only call on the name of the LORD (ie, YHWH, "Jehovah") and were forbidden from calling on the names of other gods, Josh 23:7.
Indeed, we have the very significant instruction in Joel:
Joel 2:32 - And everyone who calls on the name of the LORD will be
saved; for on Mount Zion and in Jerusalem there will be deliverance,
as the LORD has promised, among the remnant called by the LORD.
This, with other instructions and probations above means that YHWH ("Jehovah") was the only Savior to whom the Israelites were to pray and seek salvation. Isaiah says this explicitly several times in Isa 43:3, 11, 14, 44:24, 45:17, 21, 49:7.
This makes Paul's instruction especially significant:
Rom 10:8-13 - But what does it say? “The word is near you; it is in
your mouth and in your heart,” that is, the word of faith we are
proclaiming: that if you confess with your mouth, “Jesus is Lord,”
and believe in your heart that God raised Him from the dead, you
will be saved. For with your heart you believe and are justified,
and with your mouth you confess and are saved.
It is just as the Scripture says: “Anyone who believes in Him will
never be put to shame.” For there is no difference between Jew and
Greek: The same Lord is Lord of all, and gives richly to all who
call on Him, for, “Everyone who calls on the name of the Lord will
be saved.”
Thus, Paul is teaching that
- the confession "Jesus is Lord" is the source of personal salvation
- Jesus is the only Savior, see also Acts 4:12
- There is only "One Lord", namely Jesus
- Everyone who calls on the name of the Lord will be saved
Thus, Paul identifies the "LORD" of Joel 2:32 as Jesus. This is also confirmed by an almost identical comparison with Acts 2:28 in Peter's sermon. See also Acts 22;16, 1 Cor 1:2, etc.
APPENDIX - LORD of the OT is Jesus in the NT
There are many times where YHWH in the OT is identified as Jesus in the NT, here is a sample:
- Deut 32:43 (LXX) vs Heb 1:6
- Ps 31:5 (Eccl 12:7) vs Acts 7:59
- Ps 34:8 vs 1 Peter 2:3
- Ps 45:6, 7 vs Heb 1:8, 9
- Ps 68:18 vs Eph 4:8
- Ps 102:25–27 vs Heb 1:10–12
- Isa 8:13 vs 2 Peter 3:15
- Isa 40:3 vs Matt 3:3 (cf v11), Mark 1:3, Luke 3:4, John 1:23
- Isa 45:23 vs Phil 2:10, 11, Rom 14:11
- Isa 52:6 vs John 4:26
- etc
We also have numerous places where people prayed to Jesus such as John 14:13, 14, Acts 1:24; Acts 7:59, 60, 9:5, 10-14; 1 Cor 1:1, 2, 16:22, 2 Cor 12:8, 9, 1 Tim 1:12, Rev 5:8-13, 22:20; 1 Thess 3:11-14, 2 Thess 2:16, 17.