Should I Fabricate Additional Support Document after UK V 4.2 (a) +(c) refusal

Although your refusal was a V 4.2 (a) +(c) for which we have an excellent canonical located at UK visa refusal on V 4.2 a + c (and sometimes 'e') which you must absolutely read, since your question is compounded by a proposal to commit what is essentially fraud, I will add a little to it and actually combine liberally from Gayot's [to whom thanks] different answers.

V 4.2 The applicant must satisfy the decision maker that they are a genuine visitor. This means that the applicant:

(a) will leave the UK at the end of their visit; and

(c) is genuinely seeking entry for a purpose that is permitted by the visitor routes (these are listed in Appendices 3, 4 and 5); and

a+c is a bad situation because it is not just a question of them doubting you have the financial ability in which case you would likely have been refused on 4.2 (e), a refusal which can be more easily remedied. Rather it is akin to saying you will abscond and/or are not credible.

What these people are asking you to do, this fraud will push you into Refusal of entry clearance or leave to enter the United Kingdom under 7A

(7A) where false representations have been made or false documents or information have been submitted (whether or not material to the application, and whether or not to the applicant’s knowledge), or material facts have not been disclosed, in relation to the application or in order to obtain documents from the Secretary of State or a third party required in support of the application.

Once that happens, upon your next application it says a prior refusal under Paragraph 320 (7A) is automatically considered under Paragraph 320 (7B) the next time...

(7B) where the applicant has previously breached the UK’s immigration laws (and was 18 or over at the time of his most recent breach)by: (d) using Deception in an application for entry clearance, leave to enter or remain, or in order to obtain documents from the Secretary of State or a third party required in support of the application (whether successful or not);

And 7B spells DOOM. Under this Paragraph, the ECO has the option but not the obligation, to impose a ban. Maybe he will, maybe he won't, but the risk is usually unacceptable unless the applicant is represented by an established solicitor with a nationally recognized practice area in representing clients who have been refused for deception.

CONCLUSION

In summary, I would not recommend you apply now because nothing has changed in the short term and typically nothing changes in the short term. Finally definitely do not follow the suggestion they have given you to commit fraud.