Messaging Error Codes starting with two (2xxx) indicate that the problem is with the destination address.

2002 – Can’t send messages to this recipient because they blocked you.

1. This exception is thrown since the recipient blocked the channel. Check the “Messaging Consent Status” of the Messaging End User to resolve this issue.

The “Messaging Consent Status” of the Messaging End User shouldn’t be “Opted Out”.

Reference Article:

https://help.salesforce.com/s/articleView?id=sf.messaging_error_codes.htm&type=5

2. Please check with the end users whether they blocked the number by mistake on the Handset(Mobile Phone) level.