Problem in reconfiguring microbits radio maximum transfer units for long strings

Greetings in the mighty name of our Lord and Saviour Jesus Christ. Amen!

I am trying to write a program to allow 2 microbits to communicate with encrypted text. However, the length of the characters during radio transmission goes beyond 60 characters and part of it gets truncated before decryption can even be done by the receiver. Please, I want to find out how one can reconfigure the radio transfer limit to extend towards 70 characters at a time using C/C++.

Thanks and God bless you. Amen!