DrDatasalad 
Hello,
my job is to develop hard- and software for embedded applications.
Working now with SAM-µCs I have encountered some problems, that neither datasheet nor internet research could solve.
And normally I don't have the time to wait for over a week to get an answer.
Is there any help from professionals available?
What are the costs for telephone assistance?
Does anyone have some advice / experience where can I get help too?
awneil 
Does your company have an FAE contact?
If not, you could seek help from your distributors.
Have you looked at the 'Design Support' options on the Microchip homepage?
To raise an Issue direct with Microchip support, go to
https://microchipsupport.force.com/s/
You need to log in (creating an account is free)
https://microchipsupport.force.com/s/article/How-to-submit-a-case
I have encountered some problems, that neither datasheet nor internet research could solve.
And normally I don't have the time to wait for over a week to get an answer.
Is there any help from professionals available?
What are the costs for telephone assistance?
Does anyone have some advice / experience where can I get help too?
IMNSO, Internet forums are your most useful resource. Ask, and maybe you'll get answers.
Unfortunately, expertise tends to be scattered, so you may have to ask several places. (Here, ARM forums, Microchip forums, Arduino forums, eevblog, Adafruit Forums, Quora, stack exchange...) (different forums have different "personalities", and people decide that they "can't deal with all the snobs on X", but are ok with "the elitists on Y", and so...) You got your answer on ISRs pretty quickly, right?
Does your company have an FAE contact?
If not, you could seek help from your distributors.
This is probably the official answer. If you're a big enough customer, and your local people are good enough to answer your questions. Of course, the best people are probably in the busiest areas, with more demands on their time from other customers. The nice part of online is that questions are "scattered" to "multiple servers" and answers are "gathered" in one place, while an FAE is a "single server" that "gathers" multiple questions, and doesn't broadcast the results...
awneil you may have to ask several places
If you do ask the same question in multiple places - known a "cross-posting" - do be sure to make it clear that you have done so! Always post links between the posts, and keep them all updated.
Otherwise you will waste people's time as they answer in one forum, unaware that someone else has already said exactly the same thing in another forum!
And pay attention to the different forums' facilities for giving credit, marking issues as resolved, etc.
For example:
You got your answer on ISRs pretty quickly, right?
See Tip #5 in my signature for how to mark the solution:
DrDatasalad Hi awneil,
Thanks for your advices.
Does your company have an FAE contact?
- You mean FAE contact to Microchip?
If not, you could seek help from your distributors.
- I will try to get to know the distributor FAE.
But as there are so many processor types are out there it will be low possibility for indepth help.
- Also it takes sometimes several days to get an answer. Often you have to invest more time in getting help than it
actually helps.
Have you looked at the 'Design Support' options on the Microchip homepage?
- Yes, some time ago, but somewhere I got stuck. With the next hard problem I will try this option again
awneil - You mean FAE contact to Microchip?
Yes.
This does tend to be reserved for "key customers".
I will try to get to know the distributor FAE.
But as there are so many processor types are out there it will be low possibility for indepth help.
No, that doesn't necessarily follow.
Make sure you choose a specialist distributor with good technical support.
But none of this is really specific to Microchip - it is all pretty much the same across the industry.
