Prospective job offer

I  have signed an employment offer for a company in Oman, 6 weeks previously. they have processed an employment visa, for collection at Muscat airport.
however I was delayed leaving my previous position and since then, another international company has offered a better long term prospect, except the initial placing is in Oman.
Due to the previous company having already processed a visa, does that mean I could not accept the 2nd company offer, even though I hadn't yet mobilized and/or started work yet ?

As long as there is a visa issued in your name and passport number, there cannot be a second visa issued matching the same.

It is not an uncommon practice for many employers to apply for a visit visa and deposit it in the airport without even the person's knowledge - after the employee quits and leaves - just to spite them and to disallow their entry back into the country. Well, this was before the 2-year rule came into effect. Now the government is doing it equally effectively !

Follow your heart .and dont get confused..