Invalid numbers 

A number was provided that cannot be a real phone number due to wrong format or is ambiguous e.g. because no country prefix was provided and the number itself could belong to several countries.

Examples:

• +5456545451515544 - too long
• 5464654 - country prefix not provided - will only work if the default prefix from user settings fits the intended target country.
• +31fgf6464w54 - contains letters

Inactive numbers

An inactive number is a valid phone number, which is permanently or temporary not active and cannot receive SMS or calls.

Examples:

• Phone is switched off 
• Phone has no reception
• Phone was cancelled/deactivated by the MNO