Multi entry visa / sponsorship

Hi,

I'm a UK resident and currently out in Saudi on a 6 month multiple entry work visit visa.
I own my own company back in the U.K and hire myself out to other companies.

I was working for a company in Saudi  end of last year 2017.
We started an Application for the multiple entry work visa under that company (sponsor company in Saudi), they produced the Letter of invertation and I myself had to submit a support cover letter in my companies name registered in the U.K.
Sent to agent in UK.
The visa was granted.

I come out to Saudi completed 4 weeks work went home.
The company no longer had any work for myself in Saudi.

I was contacted a month later by another company who have work in Saudi and asked if I could come out for an interview and some training.

I accepted the offer, done some training, interview etc.
I have tried to leave the country and immigration stoped me.

The company I was working for before have put a blacklist marker on my passport while out here.

I have been in touch with the previous company to lift the blacklist mark so I can exit.
Now they are wanting me to sign some documents first! I don't know what.
I work for myself hiring myself out to different companies.
When there is no work I go elsewhere.

I will be returning back to the UK cancelling there visa and applying for new visa with the other companies sponsorship.

I will be wanting to return to Saudi with this new company.

Just looking for some advice.
Is it possible to be blacklisted like this?
Should I even sign the documents?

Thanks

Taz