WhatsApp uses your phone contacts to send and receive messages and calls. In case you are using an enterprise number with a different country code prefix than your mobile number, WhatsApp will automatically add the enterprise number country code to the contacts that are missing a country code prefix.
For example: My mobile number is in Singapore (+65-9-XXXXXXX) and I’m using a UK enterprise number (+44-7520-XXXXXX) . Some of my phone’s contacts are listed without the Singapore country code prefix (+65). One of them is “John Doe” , who is listed with the number 9-XXXXXXX. WhatsApp will automatically add the +44 country code to that number. John Doe’s number will be incorrectly treated as +44-9-XXXXXXX, rather than the expected +65-9-XXXXXXX.
To overcome the misrepresentation:
Review your contacts and manually configure the mobile numbers which are in a local format to an international format.
For example: John Doe’s mobile number should be changed from “9-XXXXXXX” to “+65-9-XXXXXXX”.
More info: https://faq.whatsapp.com/en/general/21016748