A dial-a-dealer cocaine service operating out of Sydney's CBD has been smashed, with more than 30 people arrested in a two-month operation that resulted in 120 charges being laid.

Police allegedly seized 468 grams of cocaine and 196 grams of MDMA, as well as two loaded firearms and more than $120,000 in cash. Several cars and mobile phones were also seized.

Operation Northrop was established in September to investigate the distribution of drugs, mainly cocaine, through a number of syndicates in the CBD and surrounding suburbs.

Detective Chief Inspector Stuart Bell, commander at the Redfern Region Enforcement Squad, told a press conference on Friday that the syndicates would deliver drugs to customers after receiving a call or text.