Local television station KRDO-TV reports Wyatt signed a wedding video contract with a Texas-based company called Copper Stallion Media and paid US$1800 (NZ$2900) upfront.
Montney reportedly left a negative review on the company's page on popular wedding directory The Knot.
The page has since been taken down.
According to US media reports, Copper Stallion Media threatened to sue Montney for defamation after he went to the media and posted the negative comments.
It said the couple had signed a legally binding contract on November 29 last year.
CBS reported the company accused Montney of creating a "smear campaign" and had been flooded with calls, emails and comments online.
"But have you guys ever heard of decency at all?" he reportedly said in one message to the videographers.
"You guys are disgusting, I hope your company burns to the ground."
In screenshots of its replies to comments on The Knot before the page was removed, Copper Stallion Media said it understood the bride-to-be had died but "the client and her fiance signed a non-refundable contract".
It also cited "financial strain on all wedding businesses" due to Covid-19 and an inability to afford the refund.
However, Montney said he messaged Copper Stallion Media in February, "before Covid was even a part of this issue".
"We're just putting out the facts that have happened so far," he said.
Copper Stallion Media's social media pages have been disabled or set to private.
FIANCE'S TRIBUTE TO BRIDE-TO-BE
Montney shared a "difficult" post about Wyatt to Facebook after her death in February.
"Her love, kindness, and exuberant emotions taught me how to express myself and show the world how I am truly feeling," he wrote.
"Most importantly she was my shining example of family unity.
"She showed me that it's okay to love everyone and important to let each and every person I love know it as much as possible. No words can describe and nothing in the world can change how much I loved her.