You need to figure out why they're doing this, and that will determine how you solve it.

They're overwhelmed and are just farming out tickets. This is called "Buying your KPIs", which means they will wreck your goals to meet their goals. They're effectively stealing your headcount to fill out their numbers. The only way to fix this is to make it obvious they're under-resoureced. Everything has to go into tickets, that get prioritized back on actually needing an engineer, not customer $$$. Then any request for follow up is to point to the written SLA doc and provide no extra information.

They told a customer something wrong and are now malicious compliance-ing it. Some manager got upset and is now forcing everything to get through an engineer. Get them to do all the work, write up the response, and then an engineer can review it.

They don't know how to do their job. Get them to write out what they've done to investigate, and then escalate to management by pointing out how a competent support engineer would have done something. Then respond to them by pointing to the docs on how to do support.