When a sale person is creating a quote or sales order, if they add a particular line item I need them to also select one mandatory item from a list of options.

For example, if they select "Motorola Contract Mobile Phone" they must be prompted to select one tariff from a list of products, e.g. "Anytime 500", "Anytime Unlimited", "Business Plan 1", etc. "Motorola Contract Mobile Phone" must never be in a quote/sales order without an associated tariff line item.

How do I configure this in Odoo? I considered product variants but I need to add the tariff as another line item (with cost) rather than a modification of the original item.

Thanks.