Back & forth for weeks for a simple claim - poor customer service

I have a claim for medication being rejected without a clear valid reason.

The rejection code 689 which as per my understanding it's being rejected because i did not use "network pharmacy".

I have provided the reason for this that I was discharged from hospital at after 9pm there's no way i could have looked for a network pharmacy at that hour, so i am not sure why can't simple logic be used here? what must we do when "network pharmacies" are not available late at night?

So we being going back and forth on this, I don't want to burden CMS about this as it's not necessary but this platform is my last try to resolve matter before i lay a formal complaint with CMS.