Don't trust Visa agents...
I find it quite unfair of you to state this, using the plural "...Visa agents...", essentially tarring all agencies in VN with the same brush. Long-time members of the expat.com Vietnam forum have identified, used, and referred other members to agencies which have proven themselves trustworthy.
We have received no negative reports from members we have referred to these agencies, and at this point we consider those agencies to be above reproach. No members of the forum have any monetary interest in referring people to a trusted agency. It is done only to offer assistance to fellow expats/tourists/travellers.
"Don't trust Visa agents". You're new here, and upon joining the expat.com VN forum it was obvious from your questions that your knowledge of VN visas was limited. Members were obliging and answered your questions to the best of our ability/knowledge. I must ask. Precisely how many agents have you had experience with in VN? I submit that the answer is... one. Your blanket statement is uncalled for.
... I had the worst experience with Agent and Danang immigration at the airport section.
I've read your synopsis of the experience you had at Da Nang Int'l airport, here. You apparently overstayed your visa by 4 days, and the immigration officer refused to accept your explanation for the overstay. The officer was completely operating according to immigration protocol by imposing a fine for this overstay.
Did you think that because you held another eVisa (which would have allowed you to do a border-run, 4 days prior, that is) that this would permit your staying beyond your eVisa's "valid until" date? The fact that you showed the officer your new eVisa, which you acquired while still in Vietnam, certainly didn't help matters. This is known as "visa stacking". Had you exited 4 days prior and reentered with that new eVisa, I have little doubt that your reentry to VN would have been uneventful.
Further, you stated that there was damage to your passport. This, in and of itself, is reason enough to deny your exit from VN and subsequent denial of entry to your destination country. Why didn't you arrange with the Australian embassy/consulate to have your passport replaced? I'm forced to say that the responsibility for this falls on you.
Reading your report on your unfortunate experiences, I'm still not able to understand how the agent you used was at fault in any of this. As I see it, the agent arranged for you to secure a new eVisa, which would certainly have simplified a border-run, had you done that 4 days prior. Where do you find fault with the agency you used? Did you think/hope that they would be able to persuade the immigration officer(s) at Da Nang Int'l Airport to ignore your transgressions? If so, you've vastly overestimated any agency's ability to "pull rank" over border officers.
Both officers have denied me to fly to UK from Da Nang airport.
As is their authority to do so. For any reason, and without obligation to provide you with an explanation. Such is their authority, granted to them by the state, in their own country.
There reason by immigration female was I was 4 days overstay when I was in my right to fly as long as I paid my fees to the UKÂ Â Â Â -@Eile
Firstly, you most certainly were not "...in my right to fly..." without being granted passage by immigration. In fact, the only "rights" any of us have in VN are those rights granted to us by the VN gov't. Period.
Secondly, you state "...as long as I paid my fees to the UK". I have no idea what you are trying to say with is. How does paying monies to the UK gov't have anything at all to do with your receiving fines from VN immigration for your 4 day overstay, or damage to your Australian passport?
This is the second time you have used "...by immigration female...". What does the officer's gender have to do with your being in contravention of VN immigration laws/regulations, and being called out on it? It makes you sound misogynistic.Â
If you were booked/scheduled to fly to the UK 4 days after your visa's expiry date, and since you already held a new eVisa which would have permitted your reentry to VN, why didn't you do your border-run? I assume it was due to financial concerns, and your thinking it easier to overstay 4 days, with an "explanation", of course.