Only 50 messages per hour: upgrade to send more?

Since signing up to PHPList in 2010, I now send many fewer emails than I used to. Last year, I downgraded to a ‘free’ account with a limit of 300 emails per month. The last campaign I sent (in July) only reached some subscribers after a week (I only knew this because I received emails noting that the information was out-of-date when they got it). Just sent another campaign today (Oct 19th 2017) and checked on progress. I see the following (screenshot) which suggests I need to upgrade my account to get around this limitation. I understood that the ‘free’ account would allow for the relatively small number of campaigns (and subscribers).

I’ve searched the manual and read other posts on the forum regarding limitations on the ‘messages per hour’, many of which mention amending ‘config’ settings. I’m using the web-hosted v.3.3.1 version. Have looked in the the configuration settings, but don’t immediately see anything that pertains to the number of messages or the frequency with which they can be sent.

Can anyone explain (preferably in non-too-technical terms) if and how I can get around this problem?

Thanks in advance.

As you are using the hosted service, your first call should be putting a support ticket in though your admin package I think.