Magento2 – Remove Billing Phone Field

If you plan to make the second field mandatory for the checkout, you should make it mandatory in the customer add/edit address form for consistency.

For the client side validation you need to edit each template that holds an address for and add required-entry class on the second row. Here are the templates I found for this:

• customer/form/address.phtml
• customer/address/edit.phtml
• persistent/customer/form/register.phtml
• customer/form/register.phtml
• checkout/onepage/billing.phtml
• checkout/onepage/shipping.phtml
• paypal/express/review/address.phtml
• persistent/checkout/onepage/billing.phtml

As for server side validation you need to copy the file

app/code/core/Mage/Customer/Model/Address.php to the local folder /app/code/local/Mage/Customer/Model/Address.php. You cannot extend this class because the class is never instantiated.
And you need to add something in the validate method.

After this section:

    if (!Zend_Validate::is($this->getStreet(1), 'NotEmpty')) {
        $errors[] = Mage::helper('customer')->__('Please enter the street.');
    }

Add the validation for the second row

    if (!Zend_Validate::is($this->getStreet(2), 'NotEmpty')) {
        $errors[] = Mage::helper('customer')->__('Please enter the correct street.');
    }

To validate number you can use validate-number in your module checkout_index_index.xml file.

Like ::

<item name="telephone" xsi:type="array">
    <item name="config" xsi:type="array">
    <item name="tooltip" xsi:type="array">
        <item name="description" xsi:type="string" translate="true">For delivery questions</item>
    </item>
    </item>
    <item name="validation" xsi:type="array">
        <item name="min_text_length" xsi:type="number">10</item>
        <item name="max_text_length" xsi:type="number">10</item>
        <item name="validate-number" xsi:type="number">0</item>
    </item>
</item>