What is the effect of replicated FTP port Nos on data traffic?

The question I have is strange. I however request your understanding since the area of network security is new to me. Supposing an administrator modified a port number of an FTP port by say, changing 21 to 23, which is the number of Telnet; finishing the modification would create a pair of No. 23 ports. Would this outcome on an FTP port interfere with data traffic? Your helpful advice/opinion is highly welcome.
