Staybet Casino - Refusing withdrawal due to retrospective change of bonus rules

I made a deposit (2017-08-03) of 2000 SEK with a 100% deposit bonus. I wagered the bonus playing Jackpot 6000 and Zombies, ending up withdrawing 19012 SEK. After over 6 weeks (after repeated contacts with them) they claimed I have breached the wagering rules. They said that the rules regarding Jackpot 6000 has been there since I registered (2016-11-27), I claim that they have added it recent since I always check rules carefully. I looked at copies of the site (wayback machine) from Jan 2017 (latest version of stored terms and condition), where the rules regarding jackpot 6000 was not included.
The only rule that exists regarding Jackpot 6000 was
"Please note: Bets on the following games do not count towards the wagering requirements:
Table Games, Poker Games, Slot games with progressive jackpots, Mega Joker, Jackpot 6000, Video Poker, Champion of the Track, The Wish Master, Devil's Delight, Dead or Alive, Reel Steal, Blood Suckers, Steam Tower, Creatures from the Black Lagoon, 300 shields, Pearls of India, Eye of the kraken, Pimped, Royal Masquerade, Holiday Season and Castle Builder
"

In todays version of the rules, where thay claim Date of issue 2016-12-14, they have added at the end:
"Staybet reserves the right to terminate winnings if wagering with a bonus is made on games with progressive jackpots, Mega Joker, Jackpot 6000, Video Poker, Champion of the Track, The Wish Master, Thunderstruck, Devil's Delight, Dead or Alive, Reel Steal, Blood Suckers, Steam Tower, Creatures from the Black Lagoon, 300 shields, Pearls of India, Eye of the kraken, Pimped, Royal Masquerade, Holiday Season, Medusa, Ninja Magic, Jack and the Beanstalk and Castle Builder"

If needed, I can post my mail corespondance, but it is in swedish.

Below is the linke of terms and condition from Jan 2017 I found at wayback machine.
Note that on their current terms and condition ( https:­//w­ww.s­ta­ybe­t.c­om/­en/­ter­ms-­of-use ) they claim it was last uppdated 2016-12-14.
https:­//w­eb.a­rc­hiv­e.o­rg/­web­/20­170­111­201­244­/ht­tp:­//s­tay­bet.co­m:8­0/e­n/t­erm­s-o­f-use

/Anders