verb
BAD : The porter insisted to help us with our baggage.
GOOD : The porter insisted on helping us with our baggage.
GOOD : The porter insisted that he (should) help us with our baggage.
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insist on ( doing ) sth : 'He insisted on paying for the meal himself.'
insist that sb ( should ) do sth : 'He insisted that he (should) pay for the meal himself.'