Who ya gonna call? Rob Kardashian makes waves with pregnant fiancée Blac Chyna when he tries to go through her phone in Rob & Chyna's series premiere on Sunday, September 11, as seen in Us Weekly's exclusive sneak peek.

The E! series' preview clip shows the Keeping Up With the Kardashians mainstay lounging on the bed with Chyna's phone when she gets a number of text messages.

"Who's this hitting your phone over and over?" Kardashian, 29, asks. "And your password's not the same as it was."

When the makeup artist, 28, questions why he doesn't trust her, Kardashian fires back, "It's not about that — it's just that I don't get why you even care if I go through your phone.… I mean, don't you think that's shady?"

For her part, Chyna can't seem to figure out what the Arthur George sock designer could think she is up to. The model, who shares 3-year-old son King Cairo with ex-fiancé Tyga, is expecting a girl with Kardashian later this year.

"I don't even understand why Rob would even think that I'm doing anything wrong," she tells the camera. "I'm four months pregnant, I have two businesses that I'm running, I'm with King, and I literally don't leave the house. So what could I possibly be doing?"

KUWTK's Sunday, September 4, episode featured Kardashian's sisters encouraging him to patch things up with his paramour after the engaged couple's blowout fight.

Watch the tense clip in the video above. Rob & Chyna launches on E! Sunday, September 11, at 9 p.m. ET. 

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