> For the complete documentation index, see [llms.txt](https://docs.fieldmotion.com/fieldmotion-api-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fieldmotion.com/fieldmotion-api-docs/customer/_checklandlineisunique.md).

# \_checkLandlineIsUnique

Check is a customers landline number is unique.

### Parameters

#### id

The id of the customer.

#### landline

The customers landline number.

### Example

```
FM_api('Customer_checkLandlineIsUnique', [
    'id' => '1', 
    'landline' => '02841753939'
    ]
);
```

### Result

#### On Success

```
{"ok":1}
```

#### On Failure

If the "id" parameter is not set or less than 1:

```
{"error":"invalid or missing parameter: id"}
```

If there's another Customer with the same Landline number:\
(The ID and name of that customer are returned in this result)

```
{"ok":0,"data":{"id":682785,"name":"A Test Customer"}}
```