Double deduction from my savings account

Few weeks ago they deducted a duplicate transaction from my account. according to them the problem would have been fixed in a week. i waited almost 3 weeks for them to fix it. Now it happened again that they did a duplicate deduction on my account. They cant even direct me to the correct department when i phone them and now they want me to complete forms again and wait again for a week which will then become 3 weeks again. I honestly is considering to close my account and go over to another bank. Every second or third week they are *****ing my money by the looks of it. I have a savings account and i don't have a overdraft facility but now my account is suddenly in an overdraft.