Cherelle says Griner -- who recently had her detention in Russia extended yet again by a court in the foreign country -- tried calling nearly 12 times on Saturday, but did not get through to her, according to the Associated Press.

Cherelle says she's "very pissed" over it ... because the call had been scheduled for close to two weeks, and she had been told it would go through. And, it obviously meant the world to her -- as she's still yet to hear Griner's voice since the basketball player was taken into custody back in February.

But Cherelle says the U.S. government dropped the ball ... and didn't staff someone to work the phone on Saturday -- leaving all 11 of Griner's calls to go unanswered.

"I was distraught. I was hurt. I was done, fed up," said Cherelle, who told the AP that she later learned that the phone line is generally only staffed on weekdays, not weekends.

Cherelle said a contact from the State Department apologized to her for the mishap. The AP, meanwhile, reported the State Dept. said in a statement it's "aware of the issue and was looking into it."

However, despite the apology, Griner's wife said she's now very skeptical of the government moving forward ... saying she has "zero trust" in U.S. officials at this moment.

"If I can’t trust you to catch a Saturday call outside of business hours, how can I trust you to actually be negotiating on my wife’s behalf to come home?" Cherelle asked. "Because that’s a much bigger ask than to catch a Saturday call."

Cherelle -- who previously said she was hoping to personally meet with Joe Biden over Griner's status -- said she's losing faith that that meeting will actually go down now.

"At this point," she said, "it's starting to feel like a no."