Undertaking form signed by boy side. But they are not willing to settle peacefully.

Dear Client,
If a boy’s side failed to refund the Mandapam advance after the marriage is called off the affected party can follow the legal procedures under the Indian Contract Act, 1872 & Specific Relief Act 1963. Undertaking form is a legal and enforceable contract that provides resort to legal notices, court proceeding and damages in the event of breach. In the event that the boy side continues to defy the terms of the contract, there is a necessity of seeking legal redress through filing a civil case so that the boy side may be compelled to fulfill his obligations as provided in the contract and there main any sundry losses. To overcome this challenge, it is necessary to seek the service of a civil litigation attorney to lead the party to court. However, the undertaking form is a legally binding document and non-cooperation means a breach of the contract that can be pursued through legal processes.

Hope you find this answer beneficial for resolving the dispute.

Dear Client,
Suppression or abatement of material facts is itself a criminal offence and illegal in the eyes of the law. So, any MOU or agreement even if executed between the parties cannot legalize an illegal matter and cannot be a subject matter of a valid contract or agreement and is void ab initio being infruactuous and unenforceable under the law. This is the reason behind the non-cooperation of the groom's family. If you possess any cogent evidence about the loose character of the groom or he is involved in an illicit relationship, then you can initiate a criminal prosecution against him for cheating under Section 318(1) of BNS or for giving false information suppressing material facts under Section 240 of BNS(Bharatiya Naya Sahitya). However, you can serve a legal notice which may work or may not work.

Dear client,

If you have a valid agreement between you and the other side , and if such clauses are being added then you need to review them.
If such undertaking was a valid legal document then in that case , first send them a legal notice. If they are not responding then you can file a Suit for Recovery of Money. Contact an advocate for reviewing the agreement or the form.