Talks to try to resolve one of the rail disputes at Govia Thameslink Railway will be held at ACAS tomorrow.
One thousand station and ticket office staff are due to strike next Wednedsay.
New proposals over closing booking offices will be discussed at Southern, Thaneslink and the Gatwick Express.
A two day strike by guards at Southern is also planned for next Wednesday and Thursday. It is not thought talks are planned on this.
Meanwhile a strike ballot by drivers in another dispute at the company has been called off after GTR threatened High Court action saying it has not been conducted properly.