Dino called someone but they didn't pick up. Brain is relieved saying they can forget about the call. Dino notes the person they tried to call is calling back. Brain urges Dino to ignore it.
I see it as an anxiety thing. Like when Dino was calling that was on their terms when they were ready. Despite being only a few seconds later though, Dino is so far out of that headspace he can't bring himself to answer the phone.