Taking advantage of customers

They gave me a quotation of R38 000 for drilling 85 meters includint pump installation. But when they finished drilling they told me they wanted R10000 to install pvc, and if they dont the borehole will collapse and damage the pump. i was forced to get the extra money that i did not plan to spend, going into debt... ...nothing was communicated to me....my advise to everyone is...do not use mth drilling...you will be taken advantage of and made to pay huge amounts of money tha were not mentioned in the quotation given.