Sendgrid is breaking my product. What to do?

Hi HN,

I had a successful Show HN weeks ago of my product Serial Literature (https://news.ycombinator.com/item?id=24307752). The core of it is emailing periodic installments of classic novels to subscribers.

I use Sendgrid for the email delivery and it is currently breaking my product. I have almost 1,000 subscribers already, which translates in about 200 emails to be delivered each day. Because I am on a free trial I am limited to 100 emails per day (their copy doesn't say that, it says "Send 40,000 emails for 30 days, then 100/day forever.", implicitly saying that the daily limit is only after the 30-days period, but it's not. I see both a warning in my dashboard saying I reached the 100-emails limit and can see my requests getting rejected after the ~100th request).

The catch is, Sendgrid also doesn't allow me to upgrade! Is says my account is too young. I already opened 4 support tickets with them, to no answer at all! -- btw, they have a weird automation on their ticket system where I create a ticket with priority P1 (critical impact), as it is breaking my product, and they automatically change it to a P3 (general) right after I submit it. This is probably throwing all my requests to the end of the queue.

I just need the ability to upgrade! What should I do?

I am hoping to get some Sendgrid's team replying appealing to the "HN as customer service" that I saw working before, which I think is on-topic since my only publication and traffic source is the Show HN I mentioned.

But if that doesn't work, what should I do? I am worried that changing email delivery provider now will have some negative effect on my deliverability. Is that correct to assume? That changing providers and IP for my domain will be looked badly by spam filters?