How do we know that Paul's calling as an apostle was true?

In Romans 1:1, Paul refers to himself as a 'servant of Jesus Christ, called to be an apostle.' This declaration is backed by his dramatic transformation on the road to Damascus and his unwavering commitment to the gospel despite persecution and imprisonment. His letters, filled with doctrinal teachings, prayer, and encouragement to the churches, serve as evidence of his genuine calling. His life exemplifies what it means to be an apostle, revealing dedication and a fervent desire to fulfill God's purpose.