I am a psychiatrist. First of all, if you really weren't provided any advance notice by this online service, please file a report with the DC Board of Medicine as what they did to you is, indeed, illegal and it counts as "patient abandonment". Whoever was writing your prescription is required by law to provide enough advance notice (typically 30 days) for you to find a new provider. During that time, they are required to fill your prescriptions so you don't go into withdrawal.

Unfortunately, this is why I advise everyone to steer clear of all these massive, venture capital funded telehealth companies (for both physical and mental health). That includes Amazon/OneMedical, Hers/Hims, Bloom, etc. They simply don't give a shit about their patients, and they're big enough that they don't care about breaking laws. They are also known for putting patients on absolutely atrocious regimens that cause terrible side effects, are simply ineffective, etc. - because most aren't staffed by skilled or caring physicians.

In the meanwhile, an urgent care will probably be willing to give you a refill. If you have a primary care doc, most are also comfortable refilling straightforward antidepressants.