Check is never received after account is closed
I closed my internet account in March, and there are credits in this account which should be reimbursed. I called customer service multiple times and visited physical store once (since customer service told me it will be easier to get the check in the store). They all told me a check will be mailed to me in two weeks. But I have never received a check, and it has already been 6 months. I do not trust the usual customer service any more. How can I escalate this issue?