>Sergey you are right, but i never know if there will be any ',' in the file or not

Try

lcFileName = "Whatever.txt"
lcTempFileName = FORCEEXT(lcFileName, "TMP")
COPY TO (lcFileName) TYPE CSV FOR .F.
CSTRTOFILE(STRTRAN(FILETOSTR(lcFileName), [,], [;]), lcFileName)
COPY TO (lcTempFileName) DELIMITED WITH ';"
STRTOFILE(FILETOSTR(lcTempFileName), lcFileName, .T.)

ERASE (lcTempFileName)