Client requests for weekend work on short notice

I work in tech consulting. Our contractual agreement with the client is open-ended as it’s a labour supply agreement.

Lately the client has been requesting some of our team members to work weekends on really short notices. Most of the times the requests come in on Fridays at around 3:30 to 4pm. We push back as we deem this unnecessary since we are yonks away from the go-live of the current implementation of the system.

They then escalate to our higher ups on Mondays. Our higher ups push back but then the client gets all passive aggressive all week long and the cycle resets every week. I tried being diplomatic and asked for at least 3 days notice for those weekend work requests with full scope of required work but they flat out refuse to do so as “they won’t know whether weekend work is required until it’s the end of the working week”.

Most of client’s stakeholders are quickly becoming psychotic and it’s becoming a really toxic environment because of this.

Resigning is not an option for reasons I can’t disclose and project reassignment is almost impossible .

Any advice on this? Should I bring up the right to disconnect? Should I ring FairWork?