The phrase “One baptism, but many re-fillings” is not found in the scriptures. Sometimes denominations have a catch phrase that may not be scriptural but has a lot of meaning to that particular group. It would be best to ask those who use it.
The Scriptures do speak of “One Lord, one faith, one baptism” Ephesians 4:5. Each believer receives the Holy Spirit once. We can, however, obtain more of the Holy Spirit. Jesus taught us to pray for the Holy Spirit. “If ye then, being evil, know how to give good gifts unto your children: how much more shall your heavenly Father give the Holy Spirit to them that ask him?”
Paul encouraged followers to be “Filled with the Spirit.” (Ephesians 5:15) It would imply that you can be less than full and need to work at getting more. It is a growth process.
1 Thessalonians 5:19 says, “Quench not the Spirit.” Believers can have actions or words not in harmony with God that can diminish His influence in their life. Christians need to have an educated conscience and to follow their conscience.
The Holy Spirit is symbolized by oil. In Matthew 25:1-13 two classes or virgins (pure believers) have oil. One class runs out. They did not maintain the Spirit’s influence in their life. They receive a lesser reward.
Christians need to have personal study (2 Timothy 2:15) and fellowship with other believers who are zealous for God. We need to have an active prayer life and to live by Christian principles. If we do these things we will get more and more of the Holy Spirit.