Unfortunately we cannot merge duplicate contacts or records.
These would have to done manually.
If you have duplicate customers, we can suggest two options.
You can delete the oldest version, and keep the newest.
By doing so, you actually archive the customer (you can never permanently delete them), and they can be restored simply by opening the archived tab under customers, select the customer, and tap on restore.
You can always go to the archived customer and view their records and history.
On the newest customer, add a note in the notes field that a duplicate has been archived.
The second option is more time consuming, and that would be to re-create any jobs and records under the one that has the most history, and then archive the duplicate.
In this way, you will have all the history under one contact, and not need to refer to an archived one.