If messages sometimes do not arrive or take a long time to arrive, or when list of qatar whatsapp phone numbers sending your campaign you have lower than expected results in bounce or response, or if the message arrives "changed", all this could be an indication that your provider uses "grey routes".

How do I find a legal provider that does NOT use "grey routes"?
Ideally, you should use providers that have direct connections to all operators in your country. To ensure this is the case, ask them to give you the corresponding letter, show you the certificate, or tell you where their contract or integration with the telephone operator is published.
In addition to verifying that your provider has direct connections to the operators in your country, verify their service, seed phone numbers and randomly check delivery, as well as measure bounce and responses to your messages. Compare effectiveness between providers and ask for references before starting to work with a new provider.