I am trying to write an algorithm that takes a PCN/mobile number and converts it to its new format. Eg 0956 will become 07956, 0370 will become 07770 etc etc I have all the rule sets and have nearly got there. The problem arises because the function must be designed to accept a whole PCN
find the prefix part and find the suffix part.

eg 0956 123456 --> 07956 123456
(normal 6 number suffix and normal 4 number prefix)

but what happens when the number is 0961 4258160 here there is a seven number suffix how do we know where to chop the suffix part????

Note virtually impossible to use length as prefix lengths can be 4/5/6/7 and suffix lengths can be 6/7. Has anyone got any ideas at all?