When Dmitry Argarkov was sent a letter offering him a credit card, he found the rates not to his liking.
But he didn't throw the contract away or shred it. Instead, the 42-year-old from Voronezh, Russia, scanned it into his computer, altered the terms and sent it back to Tinkoff Credit Systems.
Mr Argarkov's version of the contract contained a 0pc interest rate, no fees and no credit limit. Every time the bank failed to comply with the rules, he would fine them 3m rubles (£58,716). If Tinkoff tried to cancel the contract, it would have to pay him 6m rubles.
Tinkoff apparently failed to read the amendments, signed the contract and sent Mr Argakov a credit card.
"The Bank confirmed its agreement to the client's terms and sent him a credit card and a copy of the approved application form," his lawyer Dmitry Mikhalevich told Kommersant. "The opened credit line was unlimited. He could afford to buy an island somewhere in Malaysia, and the bank would have to pay for it by law."
However, Tinkoff attempted to close the account due to overdue payments. It sued Mr Argakov for 45,000 rubles for fees and charges that were not in his altered version of the contract.
Earlier this week a Russian judge ruled in Mr Argakov's favour. Tinkoff had signed the contract and was legally bound to it. Mr Argakov was only ordered to pay an outstanding balance of 19,000 rubles (£371).
"They signed the documents without looking. They said what usually their borrowers say in court: 'We have not read it',” said Mr Mikhalevich.
But now Mr Argakov has taken matters one step further. He is suing Tinkoff for 24m rubles for not honouring the contract and breaking the agreement.
Tinkoff has launched its own legal action, accusing Mr Argakov of fraud.
Oleg Tinkov, founder of the bank, tweeted: "Our lawyers think he is going to get not 24m, but really 4 years in prison for fraud. Now it's a matter of principle for @tcsbanktwitter."
The court will review Mr Argakov's case next month.