To make an account Reg D compliant, can I just turn off the interest or do I need to close the account, the customer has been notified of excessive transactions

You can convert it to a non-interest bearing account type. You can't leave them in an interest bearing account type and not pay interest... that would be a truth in savings violation.

So, same account number, different account type. Redisclose the new TISA at conversion.

Or you could reclassify it from a "savings" account to an "interest bearing transaction account" that became legal under DFA on July 21, 2011.