(Sharecast News) - Long-suffering commuters in London, Surrey and the South of England were handed a dose of Christmas misery on Thursday evening, as the Rail, Maritime and Transport Workers Union (RMT) confirmed two more 24-hour strikes on South Western Railway (SWR) would go ahead during December.The union had already announced a strike on 22 December, with the new announcement confirming action on 27 and 31 December.SWR, which is a joint venture between FTSE 250 passenger transport operator FirstGroup and Hong Kong firm MTR Corporation, has been embroiled in a lengthy dispute with its workers over the future role of guards on trains.The RMT claims SWR is not guaranteeing the presence of guards on suburban services, and thus compromising safety.SWR, however, said it has guaranteed all existing guard positions, and only wants the ability to run trains without guards in certain circumstances, such as when staff are ill.The union's general secretary, Mick Cash, said the train operating company had "stubbornly refused" to ensure all trains would run with guards on board."South Western Railway are looking for a green light to throw the guard off their trains as and when they see fit in the name of profit," he said.But the rail operator has called the strikes "totally unnecessary"."By announcing further strike dates, the RMT has shown it has no intention of finding a solution and is only interested in inflicting more misery on passengers as they try to enjoy the festive season," a spokesperson for SWR said.Travellers in the North of England are also suffering similarly, with RMT members on Arriva Rail North - which trades as Northern Rail - striking every Saturday for the rest of the year in a similar dispute over the role of guards.