Definition of get onto:
(v) :
To contact a person or organisation about a particular matter.
(v) :
To connect, especially to the Internet or a network.
(v) :
(transitive) To scold someone; to pressure someone; to criticize someone.
(v) :
(informal, transitive, slang) To believe or suspect something; to understand or come to understand something; to realize something.
(v) :
(ditransitive, informal) To introduce someone to something.
(v) :
(informal) To take a look at someone or something.