bombarded with text messages

stupidly gave my mobile number when looking to hire a motorhome, big mistake at least one text message every day sometimes 2 and i cant block it because there isnt a number to block , called the number provided every 10 mins yesterday and no answer apparently all operators were busy all day , no acknowledgement of the 3 emails i sent its as if they dont exist. 4 calls today and still no answer im probably going to have to change my number now