This shift was real, and it is often mangled. Antony Flew, one of the twentieth century's most influential atheist philosophers, did change his mind late in life — but he became a deist, persuaded by design arguments, not a Christian. His book was co-written, and critics questioned how much was his; he insisted the conclusion was. A deist, not a convert to Christ — and worth citing precisely.
Antony Flew, There Is a God (2007) — in copyright; linked, not reproduced.
Sources & further reading