And several other transport unions are balloting members over possible strike action, which could go ahead in the coming weeks.
'RUTHLESS'
Transport Secretary Grant Shapps said the disruption would cause "misery" and force hospital patients to cancel appointments.
Pupils sitting exams -- including his own children -- would face extra pressures through having to change their travel plans, he said.
"The RMT is punishing millions of innocent people, instead of calmly discussing the sensible and necessary reforms we need to make in order to protect our rail network," he added.
The government is under pressure to tackle inflation and rising household bills that have left many Britons struggling to make ends meet.
But Treasury minister Simon Clarke ruled out "inflation-busting pay increases" in the public sector to avoid fuelling inflation further.
The government and rail operators maintain that modernising the network is necessary as travel use changes, particularly after the pandemic.