The simple answer to this is, no problem!
We obviously have the expertise to make these changes in our business and not having a Managed Service shouldn't be an inhibitor to getting a change made on your website.
As you would expect, not having a Managed Service does attract a fee for us to do this work for you. To try and keep things simple for everyone, we charge for our time at an hourly rate and the time is billed in 15 minute increments.
You require us to upload, format and publish a blog on your website. You supply the completed text and the image to be used on the blog along with any credentials we require to access the website.
Assuming it's a Wordpress site, this type of change would take approximately 20 minutes to make.
Based on our billing model, that would mean 2 x 15 minute increments charged at the standard hourly rate.
Over time, if we find that you're making a number of these requests and that starts to approach or exceed the entry price for our Managed Services plan, we would proactively recommend that you sign up to one to get the most value.