The Rothesay branch of the Royal Bank of Scotland is among 62 in Scotland that are under threat of closure.
The bank has said more customers are accessing services online or with mobile devices.
But the move has been criticised by union leaders.
Unite regional officer Lyn Turner said: “RBS’s 2016 annual report states that they want ‘to transform the bank into the number one for customer service, trust and advocacy’.
“What we have in 2017 is a plan which amounts to institutional financial vandalism on a scale which has never been seen in this country ever before.
“Customer service? Trust? Don’t make me laugh.”
“This is not the Royal Bank for Scotland. It’s the Royal Bank for its top directors and executives filling their boots while they devastate local communities with bank closures and destroy hundreds of quality jobs.”
Unite Scotland deputy general secretary Mary Alexander commented: “RBS has forgotten about the many people in food bank Scotland who cannot afford to take the bus to their nearest banking facility or parents with small children who do not have access to a car.
“Nor do they care much about the elderly or those in poor health who cannot travel any distance to their nearest branch.”
An RBS spokesman said: “More and more of our customers are choosing to do their everyday banking online or on mobile.
“Since 2012 the number of customers using our branches in Scotland has fallen by 44 per cent. Only 1 per cent of our customers in Scotland now use a branch regularly while the number of regular mobile users has increased by 39 per cent since 2015.”
The spokesman added: “We expect these closures to result in around 158 redundancies. We realise this is difficult news for our colleagues and we are doing everything we can to support those affected. We will ensure compulsory redundancies are kept to an absolute minimum.”