Actual expenses exceeds the Agreed Cost of Materials for Building construction

Good day to all, I am a civil engineer and recently closed a contract as a contractor of a commercial building. In our contract and during the prevailing pricing of construction materials when the contract was consummated the construction of the building based on the bills of materials amounted to P 10.0 Million, however, it turned out to be more than the first estimated cost. with this, a conflict with the owner gradually developed, because they keep on implying that there was a a bad faith/fraud on my part as the contractor of deceiving a lower cost of materials for them to enter into a contract with me. Recently they seeked a legal remedy on our dispute and charged me with ESTAFA. My question is, is there a merit on their complaint for them to sue me in court with ESTAFA? Please I badly needed your legal opinion on this. Thanks a lot!

did you abandon the job?

I did not abandoned the contract, however, the owner insisted for us to forge a MOA stating among other things that the administration of the construction be transferred to their supervision as per advised of their hired consultant....now there is mounting difference between me and the consultant coz he's feeding the owners unfounded accusations pertaining to the status and progress of the construction....

you can argue that this is a construction contract and that if it was breached, it does not amount to estafa.