Train drivers are to stage four one-day strikes in an escalating row over taxis, which could disrupt services across southern England.
SWT says Aslef wants to widen the strike action
Union Aslef has balloted 1,000 members at South West Trains over the stoppages on 28, 31 July and 11, 14 August.
They said SWT had reneged on an agreement to provide taxis for drivers on early morning or late night shifts.
SWT denies scrapping the taxi service and warned of "severe disruption" if the strikes goes ahead.
An SWT spokeswoman said some drivers had abused the taxi service.
She said the service is still available but staff will now have to pay their own tax on the perk.
"It was unfortunately treated by some like a free sweet shop," she said. "It's about taking personal responsibility."
Aslef members at Waterloo Station in south London have taken part in several strikes recently over the taxis dispute.
However the action had no impact on services after managers were drafted in to cover for drivers taking industrial action.
SWT managing director Stewart Palmer said the new round of strikes was designed to have a bigger impact than the previous ones.
"The union is clearly attempting to bolster this unsuccessful dispute by now calling strikes at other depots," he said.
"We will do everything we can to mitigate the effect of the strikes but clearly it will cause severe disruption depending on the support for the strike on the day."
SWT operates busy commuter routes in Waterloo from counties across south-west and south-east England.