A company issuing such insurance or indemnity bond shall file with the Commissioner such proof that the required insurance or indemnity bond has been issued as shall be satisfactory to the Commissioner and such insurance or bond shall not lapse, expire, or be cancelled while the registration is in force until at least 20 days' written notice has been given the Commissioner of an intention to cancel. Upon receipt of the notice, the Commissioner shall forthwith notify the insured of such intention to cancel, and that if other insurance or indemnity bond is not furnished within 15 days thereafter, the registration of the motor buses of such insured will be cancelled and the number plates of such motor buses will be taken up by the Commissioner.