Dealing with a small supplier that is really bad at replying to me.

I’ve got a small supplier (an in individual I deal with in a company of about 30 employees) that I get good deals from when they message me and sell me stuff on ad hock basis, when they have stuff they need to get rid of. I’ve been dealing with them for years however lately they are beginning to annoy me.

They have started telling me they have items then sending me an invoice before they go on leave for a few days so I pay then items don’t get dispatched for four to six days.

They are just not reply to emails. If I ask for a tracking number I’ll get an email from a carrier sending me a tracking number. Not a reply from them. Even if I email asking for a reply I’m not always getting a reply.

If I phone them they don’t pick up but then might reply to an email I sent.

I’m really getting Pi$$ed off with them. I don’t feel like I’m asking for a lot and I have £1000’s tied up in items not knowing when they will be dispatched. And dispatch it taking ages from when they message me because they have a tendency to message me before they go off for a few days.

How do I fix this without annoying them to the degree they stop selling me stuff?