Paul often uses Old Testament passages and puts them in a NT context.
Acts 2:21 - "And it shall come to pass, [that] whosoever shall call on the name of the Lord shall be saved".
Acts 2:38 - "Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost."
In verse 21, Peter says that whoever calls on the name of the Lord shall be saved. In verse 38, after being asked what they should do, Peter tells the crowd to repent and be baptized for the remission of sins. It is obvious he is telling them this is how they are to be saved. Therefore, repenting and being baptized for remission of sins and calling on the name of the Lord are equal.
Acts 22:16 - "And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord."
In this verse, Ananias equates being baptized, to wash away sins, with calling on the name of the Lord.
Here we have 2 examples of calling on the name of the Lord being used as a parallel to being baptized for the remission of sins.