Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE customers (phone_number VARCHAR, customer_id VARCHAR); CREATE TABLE complaints (customer_id VARCHAR, date_complaint_raised VARCHAR)
### Question:
What is the phone number of the customer who has filed the most recent complaint?
### Answer:
SELECT t1.phone_number FROM customers AS t1 JOIN complaints AS t2 ON t1.customer_id = t2.customer_id ORDER BY t2.date_complaint_raised DESC LIMIT 1