River City Solid Surface Costco Wholesale Granite Counters Cracked Granite Countertop, chipped seam, wrong color epoxy. They won't fix the problem or answer my emails Spokane Valley, Washington

We recently had BLACK GALAXY countertops installed by River City Solid Surface.  We found River City Solid Surface through Costco Wholesale.  We contacted Costco and they sent someone to our house from River City Solid Surface.  We wanted to pay cash, so River City asked Costco if they could accept cash.  Costco said no.  River City then informed us that they could deal with us directly and we could pay cash.  After installation, we noticed a 4 foot long line through the counter.  It goes in a perfectly straight line. It appeared to me that the counter had been broken and glued back together.  The installer assures us that it's a VEIN.  So, we are assuming he is correct. However, we also noticed a 2 inch long crack near the sink, that follows the exact path of the vein.  We are worried that it will continue to crack along the vein.  We asked the installers to come and look at it.  When they got there, I showed them how I could catch my fingernail on the crack.  I asked them to do the same.  They both just felt it with the PAD of their fingers, and denied feeling a crack.  I again asked them to use their fingernails, and they again just used the pads of their fingers.  It was like they didn't want to know it was there.  I even took pictures of the crack, and it shows up fine in the pictures.  I emailed the pictures to them, but now they aren't responding to my emails. Also, we had a problem with the SEAM.  The seam has about 5 places where there were chunks or chips of the edge broken out.  So, in places the seam is a little over 1/8th of an inch wide, and in one place in the back, there is a chip that is a half inch wide. This gap is over twice the width of industry standard, which is 1/16th of an inch +/- 1/64th of an inch.  It is also not even along the edge.  It appears that their saw was DULL when cutting the edge.  Also, it is more of a white or grey color that they used on the seam epoxy, and should be closer to the black color of our counter.  I also sent them pictures of the seam.  Again, they won't respond to me. We are requesting a written warranty stating that they will replace the counter if the crack expands any further.  Also, we asked them to either fix the seam or give us a credit for the seam.  Again, no response to my emails.  Simply horrible customer service.