On top of that, the transaction fee to the customer, which started out at £1.50 is now up to £1.80.
"Although it went up they didn't increase my commission; in fact, they didn't even tell us. A customer came in and told me, and customers think all this money goes to the retailer."
Bank Machine also didn't communicate to her that top-ups had been added at no cost to the customer, thus hitting her PayPoint sales.
Tasnim adds that she has a crisp display in her store that earns her more money than the ATM does.
The company wouldn't comment on this specific case, but a spokeswoman said: "First, all of our contracts are relatively brief documents where each party's rights and obligations are clearly explained. While, of course, misunderstandings occur in any aspect of life, the clarity of the Bank Machine contract makes genuine misunderstandings very unlikely."
She added: "Second, the charge for a cash withdrawal of up to £250 made at this specific ATM has risen from £1.75 in August 2008 to the current £1.85 in August 2010. In percentage terms, this amounts to less than 2.9% per year."
Tasnim would like out of the contract, but this doesn't seem likely because the public relations person concluded: "Bank Machine invests upwards of £15,000 to install and operate an ATM. As one might expect, that level of investment can only be justified by having a sensible length of contract. Both parties are expected to honour the length of contract agreed."
However, the outcome is now vastly improved. Bank Machine offered to raise her commission to 18p. Tasnim said she would switch the machine off and take her chances in court. The company finally put the commission up to 35p and to 45p for transactions over 1,000.
Tasnim agreed, on the condition that the length of time on the old contract would not change. When they sent her a new one pitching for another seven years, she dug her heels in.
However, a revised new contract has now arrived with only half that time still to go. A good outcome for her and rightly so. These deals are meant to be partnerships.