The phrase "a warm call" is correct and usable in written English.
It can be used to describe a friendly or inviting phone call, often intended to establish a positive connection or relationship.
Example: "After weeks of emails, I finally received a warm call from the client, expressing their interest in our proposal."
Alternatives: "a friendly call" or "an inviting call".
"I wouldn't necessarily call it a warm call, but it was a good first encounter," an administration official said.
"This is what a cold call looks like, this is what a warm call looks like, this is what a warm letter looks like, this is what a face-to-face looks like," she continued.
You can snuggle up, when the city shifts and shivers, go home, seek refuge in a warm café, call the woman you love.
Don't put them in a warm car, and call the hotline".
But with only a handful of defections, the public gave a warm curtain call to the singers, conductor, orchestra and director.
The spokeswoman talked about a warm phone call between May and Trump on Thursday, adding: "The president-elect talked about enjoying the same close relationship that Reagan and Thatcher did.
The two leaders had a warm phone call last week in which President Obama lauded the two nations' security partnership.
Apr. 30, 2017, 12 33 p.m. President Trump placed a "warm" phone call to Philippines President Rodrigo Duterte, who has been widely criticized for a bloody anti-drug crackdown, and invited him to visit the White House, both countries said.
He and his executives put together a campaign called Sixty for Sixty, in which they recruited fans and fellow-performers to urge radio programmers to play Strait's latest single, a warm love song called "Give It All We Got Tonight".
Blanquette de veau, the classic veal stew, is liquefied to a warm cream called "veal nog" that requires a rotor-stator homogenizer and a centrifuge.
For "Autumn in New York," the duet with Ella Fitzgerald and Louis Armstrong, the app suggested painting walls Perpetual Green and doing the trim in a warm yellow called Glorious Glow and a shade of gray named — ironically, considering the song title — Silicon Valley.
