Hi. You need to reconsider your table design, as you have incorrectly separated out components of the customer table such as the customer phone into separate tables. These are simply attributes of the customer entity, and should remain as part of your customer table.
There is no need at all to add the complexity of maintaining separate customer-attribute tables joined by customer ID when a single table is all that is required.
When you come across 1-to-1 relationships such as those involved in your separated customer / customer phone tables, it is normal to combine these into the one table as long as all fields of the sub-tables are dependent on nothing other than the key of the master table - customer ID in your case.
I recognise that customers can have more than one phone number. This is dealt with by recording as separate attributes a landline number, mobile number, and fax number. If customers may be business clients you may also wish to record the business phone number in addition to their landline (home) phone number.
We have a helpful article on
database normalisation and table structures which you may find useful.
-Stewart