NatWest has announced it is halving the rate on its instant access Isa to just 0.25% for some savers, following a rate cut by NS&I.From 1 December, the rate on the NatWest cash Isa will fall from 0.5% to 0.25% on deposits up to £25,000. Investors with £25,000 to £50,000 will now receive 0.5%, down from 1%. Deposits of £50,000 to £100,000 will be cut by a quarter to 0.75% and those with more than £100,000 will see their rates unchanged.NatWest is also increasing overdraft charges on its Select Platinum and Select Black accounts, to a daily charge of £6. However, the accounts do offer fee-free overdrafts of £250 and £500 respectively.A NatWest spokesperson said: “We are reducing our NatWest Cash ISA interest rates in line with market conditions and our competitors. We have written to customers informing them of changes to their account, which will take place on 1 December, to allow them time to decide how they allocate their 2015/16 ISA allowance”.The bank also says it remain committed to promises made in 2014 that it will not offer preferential rates to new customers or offer introductory bonus rates. Moneywise Verdict:If you will be affected by the rate cut you don’t need to wait until 2016 to move your money to a better account. You’re only allowed to open one Cash Isa each year, but you can switch to another providing you transfer all the money you’ve saved this year. You’re free to move as much or as little of your Isa savings from previous years whenever you like.Virgin Money has an online-only Isa that pays 1.56% AER if your balance is £1 or higher, and accepts transfers, providing you make no more than three withdrawals a year. Nationwide customers can get a slightly higher 1.6% rate with no withdrawal restrictions. The Bank of Punjab will pay 1.65% AER, but it is a branch-only account and it has a limited network in the UK.