onDelete('cascade) not working

Hi

I Have 3 tables

1)policy (primary key)
2)project_declaration (foreign key for policy)
3)endorsement  (foreign key for policy)

when I delete a record in the policy table. The other records which are link to that table are not deleting. I am using onDelete('cascade) and I am using soft delete in all 3 tables.

my migration files

policies 

 Schema::create('policies', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->integer('controll_number');
            $table->string('customer_name');
            $table->string('insured_name');
            $table->integer('policy_number');
            $table->string('policy_type');
            $table->date('start_date');
            $table->date('end_date');
            $table->string('insurance_company');
            $table->string('policy_sum_insured');
            $table->string('premium');
            $table->string('gst');
            $table->string('total_premium');
            $table->timestamps();
        });

project declaration

Schema::table('project_declerations', function (Blueprint $table) {

            $table->unsignedBigInteger('policy_number_id')->after('id')->nullable();
            $table->foreign('policy_number_id')->references('id')->on('policies')->onDelete('cascade');

            $table->unsignedBigInteger('Brand_id')->after('contact_person')->nullable();
            $table->foreign('Brand_id')->references('id')->on('brands')->onDelete('cascade');

            $table->date('intimation_date')->after('addredd')->default(now());

            
        });

endorsement

Schema::create('endorsements', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->unsignedBigInteger('legalentity');
            $table->unsignedBigInteger('policy_number');
            $table->string('location');
            $table->string('premium');
            $table->string('gst');
            $table->string('totalpremium');
            $table->date('start_date');
            $table->date('end_date');
            $table->string('suminsured');
            $table->text('description');
            $table->text('endorsement_filename');
            $table->foreign('legalentity')->references('id')->on('legal_entities')->onDelete('cascade');
            $table->foreign('policy_number')->references('id')->on('policies')->onDelete('cascade');
            $table->timestamps();
        });