、？
If you break your promise, we're through — got it?
Literal
Promise broke-[if-たら], cutting-ties [copula-ですからね]?
やぶったら is casual past-conditional of 破る ('to break'). 絶交 (ぜっこう, 'cutting off relations') is the dramatic word for ending a friendship. ですからね？ combines the polite copula with から (reason/warning) and ね (seeking acknowledgment), creating a firm 'so you'd better understand' tone. The question mark makes it a confirmatory threat — 'you understand, right?'