How works MAX_CHAR_BILLING

[WhiteEagle]

Hey guys,
If I understand this correctly, MAX_CHAR_BILLING is a function to buy character slots.
How is this called by an item? 
To change the function for the character slot is is CharMove++.
Is there something like that for MAX_CHAR_BILLING?

#ifdef VIP_ENABLE
	#define MIN_STORAGE 300 // Default number of storage slots.
	#define MIN_CHARS 3 // Default number of characters per account.
	#define MAX_CHAR_VIP 2 // This must be less than MAX_CHARS
	#define MAX_CHAR_BILLING 5 // This must be less than MAX_CHARS
#endif

 

Edited May 17, 2020 by WhiteEagle