How to get a non-changeable bitcoin address. I tried to register on few bitcoin wallets websites but on each website btc address is changed after one payment is received and I didn't find the option to create a non-changeable one. I know that for privacy is much better to have a changeable btc address, but I need to create a non-changable btc address
With the majority of wallets, you'll be presented with a new address for each payment. As you mentioned, this is important for your financial privacy, so it is a standard practise.
That said, you can re-use an old address, and your wallet should detect the additional transactions received at that address, updating your balance accordingly.
In short: your wallet is a collection of addresses, it is not just 'the address that is currently displayed'. So you can re-use old addresses from the wallet if you so desire.