Airtel — block my husband number since I lost him in accident

Block my husband number [protected] he is nomore. But his number has been used by my in-laws. I find it inconvenient wen my friends sat tat his number his active still. His watsapp number they are still using my friends n myself get shock wen itseems online.. It really hurts and want my husband number to be permanently blocked. So block his number tat number as soon as possible