If you took possession of the phone in California the sales tax is not refundable even if you then took the phone out of the state or out of the country. See the information in https://www.cdtfa.ca.gov/formspubs/pub104/# including the following:
In general, the sale of merchandise to a resident of another country is taxable if the buyer takes possession of the item in this state—even temporarily—or uses the item before it is shipped abroad. However, some sales to foreign residents qualify as exports and are not subject to California sales or use tax. If you sell an item that will be shipped abroad before use and you ship it directly to a foreign destination or to a qualified person who will export the item, your sale may not be taxable. Please note: Foreign travelers cannot obtain refunds of sales tax paid on California purchases.